The quick answer: Many common pet health problems begin with surprisingly ordinary changes: more scratching than usual, unpleasant breath, difficulty getting up, a change in appetite, vomiting, diarrhoea, drinking more water, losing weight or simply behaving differently. Skin allergies, dental disease, arthritis, digestive problems, parasites, ear infections, urinary problems and metabolic conditions such as diabetes are among the health concerns owners should understand. Knowing what is normal for your pet makes unusual changes easier to spot. Persistent, painful, severe or rapidly worsening symptoms should always be discussed with a veterinary professional.

A dog who suddenly hesitates before jumping onto the sofa.

A cat who starts drinking noticeably more water.

The faint smell of bad breath that becomes impossible to ignore. A patch of irritated skin. A limp that appears after a long sleep but seems to disappear once your pet gets moving.

Pet illness does not always announce itself dramatically.

Often, the first clue is simply that something has changed.

That is what makes understanding common pet illnesses so useful. Owners do not need to become amateur vets or diagnose every cough, scratch and upset stomach. Far more useful is learning to recognise potential signs of illness in pets, knowing which changes deserve closer attention and understanding when to take your pet to the vet.

This guide covers the health problems every owner should have on their radar, from skin problems and dental disease to arthritis, digestive trouble, parasites, diabetes, kidney disease and other conditions in dogs and cats.

It also comes with an important rule:

Knowing the symptoms helps you notice a problem. It does not replace a veterinary diagnosis.

If your animal is already unwell and you are trying to decide whether the situation can wait, our guide to signs your pet needs a vet covers urgent warning signs such as difficulty breathing, collapse, repeated seizures, severe weakness, persistent vomiting and an inability to urinate.

For everything else, start with the animal you know better than anybody else.

How Do You Know When Something Is Wrong With Your Pet?

There is no universal "sick pet" look.

Some animals make discomfort spectacularly obvious. Others can be remarkably subtle.

That is especially important with cats, which may show illness through small changes in behaviour rather than obvious cries of pain. Dogs can also carry on eating, walking or greeting their owners despite developing health problems.

Instead of looking for one definitive symptom, look for changes from normal.

That might mean:

• eating considerably more or less than usual;

• drinking noticeably more water;

• weight gain or unexplained weight loss;

• vomiting or diarrhoea;

• coughing or altered breathing;

• unusual scratching or licking;

• hair loss or changes to the coat;

• bad breath or difficulty eating;

• changes in urination or toilet habits;

• stiffness, limping or reluctance to exercise;

• new lumps, bumps or swelling;

• unusual lethargy or weakness;

• hiding, restlessness or other behaviour changes.

Context matters too.

A single soft stool in an otherwise bright, hungry and playful dog is very different from persistent diarrhoea accompanied by vomiting, abdominal pain and lethargy.

Likewise, a senior dog taking slightly longer to rise deserves monitoring, but suddenly being unable to stand is a very different situation.

Severity, duration and combinations of symptoms matter.

Know Your Pet's "Normal"

One of the most useful forms of pet health monitoring costs absolutely nothing.

Pay attention.

You probably already know more about your animal's routine than you realise. You know how enthusiastically they normally greet dinner. You know whether they drain their water bowl or barely seem to touch it. You know how often your dog asks to go outside and roughly what you normally find in your cat's litter tray.

You know whether your pet charges upstairs or takes them slowly.

That everyday knowledge creates a baseline.

When something changes, you are more likely to notice.

Routine handling helps too. Grooming your pet, checking their coat, looking at their teeth and gums and becoming familiar with their body can make a new lump, tender area, skin irritation or other physical change easier to detect. Our pet grooming collection includes everyday coat-care and grooming essentials for dogs and cats.

That brings us to one of the most visible groups of pet health conditions.

1. Skin Problems, Allergies and Persistent Itching

Scratch.

Scratch.

Scratch.

Occasional scratching is perfectly normal. Persistent scratching is not something to simply write off as "a dog being a dog" or a cat grooming itself.

Skin problems can have numerous causes, including pet allergies, parasites, bacterial infection, fungal infection and other forms of skin inflammation. What looks like a straightforward patch of itchy skin can therefore require some detective work.

Common signs include:

• frequent scratching;

• persistent licking or chewing;

• red or inflamed skin;

• bald patches or hair loss;

• scabs or crusting;

• flaky skin;

• an unusual smell from the skin;

• sore areas;

• changes in coat quality;

• rubbing the face or ears;

• recurrent ear irritation.

Conditions such as dermatitis and eczema-like inflammation can make animals extremely uncomfortable. Fleas, ticks and mites can cause itching too, while some pets develop reactions associated with environmental or dietary allergens.

Don't Assume Every Itch Is an Allergy

"Skin allergy" has become a catch-all phrase in pet conversations, but similar-looking symptoms can have very different causes.

An itchy dog could have fleas.

Another might have a skin infection.

Another may be experiencing an allergic skin condition.

And excessive licking in one particular spot could even be related to pain rather than a primary skin problem.

That is why persistent, recurrent or severe skin irritation deserves proper veterinary assessment rather than endless trial-and-error home treatments.

Grooming Can Help You Spot Changes Earlier

Regular grooming is not a treatment for dermatitis or infection, but it gives owners a valuable opportunity to look closely at the skin and coat.

Part the fur occasionally. Look underneath.

Check areas that are easy to miss, including:

1. behind the ears;

2. beneath the collar;

3. around the armpits;

4. between the toes;

5. around the base of the tail;

6. underneath the belly.

Finding a tiny bald patch while grooming is much easier than discovering a large sore area several weeks later.

For dogs that need regular coat maintenance, our dog grooming range brings shampoos, brushes, combs and everyday grooming products together in one place.

Watch the pattern, not just the scratch. Repeated itching, recurring skin inflammation, hair loss or sore skin tells you far more than one isolated scratch ever could.

2. Fleas, Ticks, Worms and Other Parasites

Some pet health problems are microscopic.

Others jump.

Parasites are a familiar part of pet healthcare because dogs and cats can encounter fleas, ticks, worms and other parasites throughout their lives. The exact risks vary with species, age, lifestyle, location and travel history.

Fleas can cause considerable irritation and may trigger intense scratching in sensitive animals. Ticks attach to the skin to feed. Internal parasites include different types of worms, and an infected pet will not necessarily display an obvious sign that tells you exactly which parasite is involved.

Possible warning signs can include itching, visible fleas or flea dirt, changes in coat condition, digestive upset, weight loss or visible worms or worm segments, depending on the parasite concerned.

But there is a catch:

A pet can have parasites without looking obviously ill.

This is why parasite control is usually approached preventatively rather than waiting until an infestation becomes impossible to miss.

Our detailed guide to pet parasite prevention, fleas, ticks and worms explains these parasites in greater depth and discusses why prevention should be tailored to the individual animal with appropriate veterinary advice.

Parasite Prevention Is Not One-Size-Fits-All

A house cat and a dog that spends weekends crashing through long grass do not necessarily have identical parasite exposure.

Neither do a puppy and a senior dog.

Factors that may affect parasite risk include:

• access to the outdoors;

• contact with other animals;

• hunting and scavenging;

• diet;

• travel;

• local parasite prevalence;

• age and health;

• previous infestations.

Your vet can help determine an appropriate flea treatment, worming and tick-control approach for your particular pet.

And never assume that a parasite product designed for one species is automatically safe for another. Cats and dogs are not interchangeable when it comes to medication.

3. Dental Disease: The Health Problem Hiding Behind Bad Breath

Pet breath is never going to smell like mint toothpaste.

But persistently foul breath should not automatically be dismissed as normal either.

Dental problems are easy to overlook because most owners do not inspect their pet's mouth every day. Plaque can accumulate, tartar can develop, gums can become inflamed and dental disease can progress quietly.

Common warning signs of dental or oral problems can include:

• persistent bad breath;

• visible plaque or tartar;

• red, inflamed or swollen gums;

• bleeding from the mouth;

• difficulty chewing;

• dropping food while eating;

• eating on one side of the mouth;

• pawing at the face;

• excessive drooling;

• reduced interest in hard food;

• loose, damaged or missing teeth;

• apparent mouth pain.

Gingivitis and periodontal disease are not cosmetic problems.

They can cause genuine pain and deserve veterinary attention.

"But My Pet Is Still Eating"

This is one of the easiest traps to fall into.

Eating does not prove that an animal's mouth is comfortable.

Pets need to eat, and some will continue doing so despite significant dental pain. Instead, you may notice subtler changes: slower eating, approaching food and backing away, preferring softer food or chewing differently.

This makes routine dental care and periodic examination of the teeth and gums worthwhile.

At home, owners can become familiar with how their pet's mouth normally looks and smells. Depending on the animal and veterinary advice, an oral-care routine may include appropriate tooth cleaning and pet-specific dental products.

Never use human toothpaste unless a veterinary professional specifically confirms that a particular product is suitable. Products intended for humans can contain ingredients inappropriate for pets.

Dental hygiene is preventative care, not a substitute for treatment. If a tooth is damaged, gums are badly inflamed or periodontal disease has developed, a chew or toothbrush cannot magically reverse the underlying problem.

4. Arthritis, Joint Pain and Mobility Problems

A slowing pet is often described with three words:

"They're getting old."

Sometimes they are.

But age itself is not a diagnosis.

A dog becoming reluctant to climb stairs, a cat no longer jumping onto a favourite windowsill or a pet struggling to stand after sleeping may be experiencing joint pain, stiffness or mobility problems.

Arthritis—particularly osteoarthritis—is one important cause.

Osteoarthritis involves deterioration and changes within affected joints and can lead to chronic pain and reduced mobility. Although arthritis is strongly associated with older pets, joint problems are not exclusively a senior-pet issue.

Watch for changes such as:

• stiffness after resting;

• limping;

• difficulty getting up;

• reluctance to use stairs;

• hesitating before jumping;

• reduced enthusiasm for walks;

• exercise intolerance;

• altered gait;

• becoming irritable when touched;

• sleeping more;

• loss of muscle;

• reduced grooming in cats;

• repeatedly licking around a painful area.

These signs can develop gradually.

That gradual change is precisely why owners sometimes miss them.

If a dog goes from happily walking for an hour to refusing a walk overnight, the difference is obvious. If that same reduction happens little by little over eighteen months, "normal ageing" can disguise a significant mobility problem.

Weight and Joint Health Are Closely Connected

Body condition matters.

Carrying excess body weight increases the mechanical load placed on joints, which makes maintaining a healthy weight an important part of general pet healthcare—particularly for animals already experiencing mobility problems.

Nutrition should still be viewed as a whole rather than as a collection of fashionable ingredients. Our guide to choosing the best pet food for healthy nutrition explains complete versus complementary foods, balanced nutrition, feeding guidance and the role of functional nutrition.

For dogs, joint-support products also exist as part of the wider wellness market. Our Pawer Water Joint Support is one example available through It's All About Pet Lovers, but complementary products should never be treated as replacements for veterinary assessment when a dog is limping, painful or developing mobility problems.

Could It Be Hip Dysplasia Rather Than Arthritis?

Hip dysplasia is another condition owners may encounter when researching dog health problems.

It occurs when the hip joint develops abnormally, potentially contributing to pain, mobility difficulties and subsequent degenerative changes. Genetics can play an important role, and certain dogs may be more predisposed than others.

Signs can overlap with other orthopaedic conditions:

stiffness + limping + difficulty rising + reluctance to exercise + changes in gait.

That overlap is exactly why trying to diagnose joint problems from symptoms alone is unreliable.

A limp tells you something hurts or isn't functioning normally.

It does not tell you why.

Veterinary examination—and sometimes diagnostic imaging—is needed to determine the cause.

The Bigger Lesson: Look for Change Before You Look for a Diagnosis

There is a common thread running through skin disease, parasites, dental problems and arthritis.

Early signs can be easy to rationalise.

"He's always been a bit itchy."

"Her breath has always smelled."

"He's just slowing down."

"She's getting older."

Sometimes those explanations may be partly true. Sometimes they allow a developing health problem to hide in plain sight.

Good preventative pet care does not mean panicking whenever your animal has an off day. It means noticing patterns.

Ask yourself:

Is this new? Is it persistent? Is it getting worse? Is my pet uncomfortable? Are several symptoms appearing together?

Those questions become even more important with the health conditions we have not reached yet.

Because some of the next warning signs—vomiting, diarrhoea, increased thirst, frequent urination, appetite changes and unexplained weight loss—can point towards problems ranging from a temporary digestive upset to diabetes, thyroid disorders, urinary disease and kidney disease.

5. Vomiting, Diarrhoea and Digestive Problems

Few pet symptoms create quite as much immediate concern—or quite as much cleaning—as vomiting and diarrhoea.

They are also extremely broad symptoms.

A dog may vomit after eating something unsuitable. A sudden dietary change can cause digestive upset. Stress can affect the gastrointestinal system. Parasites, infections, pancreatitis, toxins, foreign objects and numerous underlying diseases can also produce vomiting, diarrhoea or abdominal discomfort.

In other words:

Vomiting tells you what happened. It does not necessarily tell you why.

The same is true of diarrhoea.

Common signs of digestive problems include:

• vomiting or retching;

• diarrhoea or unusually loose stools;

• loss of appetite;

• abdominal pain or tenderness;

• bloating or abdominal swelling;

• excessive wind;

• changes in bowel movements;

• straining to pass faeces;

• lethargy;

• dehydration;

• weight loss;

• blood in vomit or faeces.

The severity and pattern matter enormously.

An isolated digestive upset in an otherwise comfortable animal is different from repeated vomiting in a pet who cannot keep water down. Likewise, persistent diarrhoea accompanied by weakness, dehydration, pain or blood warrants considerably more concern than one unusual bowel movement.

When Does an Upset Stomach Become More Serious?

There is no single number of vomiting episodes that can safely diagnose the severity of every case. Your pet's age, existing health, symptoms and circumstances all matter.

Puppies, kittens, older animals and pets with existing medical conditions can sometimes be more vulnerable to complications such as dehydration.

Seek veterinary advice promptly if your pet appears seriously unwell, particularly if you notice symptoms such as:

1. repeated or persistent vomiting;

2. repeated or severe diarrhoea;

3. blood in vomit or stools;

4. significant abdominal pain;

5. a swollen or distended abdomen;

6. severe weakness or collapse;

7. inability to keep water down;

8. suspected poisoning;

9. suspected ingestion of a foreign object;

10. rapidly worsening symptoms.

A dramatically swollen abdomen combined with distress or unsuccessful attempts to vomit can be an emergency in dogs. Do not wait for a suspected case of bloat to improve by itself.

Dehydration Can Become Part of the Problem

Vomiting and diarrhoea cause the body to lose fluid.

When those losses continue, dehydration can develop—particularly if an animal is also reluctant to drink or immediately vomits after drinking.

Signs associated with dehydration can include lethargy, weakness and dry or tacky gums, but assessing hydration accurately at home can be difficult. If fluid loss is substantial or your pet seems unwell, veterinary advice is safer than relying on home tests.

6. Pancreatitis and Persistent Gastrointestinal Problems

Not every digestive problem is a brief upset stomach.

Pancreatitis is inflammation of the pancreas and can affect dogs and cats. Signs vary and may overlap with numerous other illnesses, which makes diagnosis based on symptoms alone unreliable.

Possible signs can include:

• vomiting;

• reduced appetite or refusal to eat;

• lethargy;

• abdominal discomfort;

• diarrhoea;

• weakness;

• dehydration.

Some cases can be much more serious than others.

Similarly, chronic gastrointestinal problems can present as recurring vomiting, diarrhoea, appetite changes or unexplained weight loss rather than one dramatic episode.

This distinction between acute and chronic symptoms is useful for owners.

Acute means something has developed suddenly.

Chronic means a problem has persisted or repeatedly returned over a longer period.

Neither automatically means "minor" or "serious." A sudden illness can be severe, while a chronic condition can gradually affect an animal's health and quality of life.

Keep a Simple Symptom Record

When digestive symptoms keep returning, memory becomes surprisingly unreliable.

Was the last episode two weeks ago or six?

Did the vomiting start before the new food?

Has your cat actually lost weight, or do they simply look slimmer after shedding their winter coat?

A basic pet health record can help. Note:

• when symptoms started;

• how frequently they occur;

• appetite and drinking changes;

• changes in stools;

• vomiting episodes;

• any dietary changes;

• new treats or chews;

• medication or supplements;

• unusual foods your pet may have accessed;

• weight changes;

• changes in energy or behaviour.

Photographs can sometimes be useful too, particularly for physical changes that disappear before an appointment.

This information does not replace veterinary testing, but it can give your vet a clearer history to work with.

7. Obesity: A Health Problem That Can Hide in Plain Sight

There is a difference between a well-fed pet and an overweight one.

Unfortunately, when we see the same animal every day, gradual weight gain can be surprisingly difficult to notice.

Obesity matters because maintaining an appropriate body condition is part of preventative pet care. Excess weight can make movement more difficult and place additional strain on joints, and weight management may form part of the wider care plan for animals with certain medical conditions.

So how do you know whether your pet is overweight?

A number on the scales only tells part of the story. Healthy weight varies enormously between breeds, body types, ages and individual animals.

Veterinary teams commonly assess body condition alongside actual weight.

Depending on species and build, an animal at an appropriate body condition will generally have ribs that can be felt without being buried beneath a substantial layer of fat and some definition around the waist. However, individual differences matter, so your vet can show you how to assess your own animal correctly.

Small Extras Can Become Big Calories

Sometimes the main meals are not the problem.

The extras are.

A treat here. A piece of cheese there. A dental chew. Training rewards. A little something from the dinner plate because somebody looked particularly persuasive.

Individually, they seem insignificant.

Collectively, they count.

If several members of the household give treats independently, it becomes even easier to underestimate the amount a pet consumes.

A few practical habits can help:

• measure food rather than estimating portions;

• account for treats in the daily food allowance;

• make sure everybody in the household follows the same feeding plan;

• monitor weight and body condition;

• provide suitable regular exercise;

• reassess portions when activity levels change;

• ask your vet for guidance if weight is difficult to manage.

Weight gain is not always simply caused by overfeeding, either. Certain medical conditions and medications can influence weight, appetite or activity.

Likewise, unexplained weight loss can be a warning sign, especially when accompanied by increased thirst, increased urination, appetite changes, vomiting or diarrhoea.

Which brings us to diabetes.

8. Diabetes in Dogs and Cats

Diabetes mellitus is a metabolic condition involving the body's ability to regulate blood glucose.

Insulin normally plays a crucial role in moving glucose from the bloodstream so it can be used appropriately by the body. When insulin is absent, insufficient or cannot work effectively, blood sugar regulation is disrupted.

Owners do not need to understand every biochemical detail to recognise an important combination of potential symptoms.

Common Warning Signs of Diabetes

Signs can include:

• increased thirst;

• frequent or increased urination;

• appetite changes;

• unexplained weight loss;

• lethargy or weakness;

• changes in body condition.

The combination of drinking more + urinating more + losing weight is particularly worth paying attention to.

However, these symptoms do not automatically mean diabetes.

Increased thirst and urination can occur with several pet health conditions. Kidney disease, hormonal disorders and urinary problems can produce overlapping signs.

A veterinary examination and appropriate testing are therefore essential.

Diabetes Requires Veterinary Management

Diabetes is not something to diagnose using symptoms or a home internet checklist.

Veterinary management may involve insulin therapy, dietary management, monitoring and regular reassessment, depending on the individual animal.

If insulin is prescribed, follow your veterinary team's instructions carefully. Never change the amount or schedule independently because a pet appears better or worse on a particular day.

Routine also becomes important.

Feeding, medication, exercise and monitoring may need to work together, which is why good communication with your vet can make managing a chronic illness much less daunting.

One symptom rarely tells the whole story. A pattern—such as increased thirst, increased urination and unexplained weight loss—is much more informative.

9. Thyroid Problems: When Metabolism Changes

The thyroid glands help regulate metabolism.

When thyroid hormone levels become abnormal, the effects can appear throughout the body.

Two terms owners commonly encounter are hypothyroidism and hyperthyroidism.

They sound almost identical.

They are not.

Hypothyroidism

Hypothyroidism means the body does not have enough thyroid hormone. It is particularly associated with dogs.

Potential signs can include:

• lethargy;

• reduced enthusiasm for exercise;

• weight gain;

• skin or coat changes;

• hair loss;

• increased sensitivity to cold.

Because these symptoms can develop gradually, they can be mistaken for ageing or simply "slowing down."

Again, symptoms alone cannot confirm an underactive thyroid. Blood testing and veterinary interpretation are required.

Hyperthyroidism

Hyperthyroidism involves excessive thyroid hormone and is an important condition in older cats.

Possible signs can include:

• weight loss;

• increased appetite;

• increased thirst;

• increased urination;

• restlessness or increased activity;

• vomiting or diarrhoea;

• changes in coat condition.

One particularly counterintuitive sign is weight loss despite eating well—or even eating more than usual.

That is the sort of change worth taking seriously.

An older cat suddenly becoming ravenously hungry is not necessarily enjoying a second youth.

It can be a reason for a health check.

10. Cushing's Disease and Other Hormonal Conditions

Another term dog owners may encounter is Cushing's disease, also known as hyperadrenocorticism.

Cushing's disease involves excessive levels of cortisol in the body and can cause a collection of symptoms that overlap with other conditions.

Possible signs include:

• increased thirst;

• increased urination;

• increased appetite;

• changes to the skin or coat;

• hair loss;

• reduced muscle strength;

• changes in body shape;

• lethargy or reduced exercise tolerance.

Notice something?

Thirst and urination have appeared again.

This is precisely why those symptoms should not be used to self-diagnose a particular disease.

A dog drinking excessively could potentially have diabetes, Cushing's disease, kidney problems or another condition entirely.

The symptom is a clue.

Veterinary testing helps solve the puzzle.

11. Urinary Problems: Changes You Shouldn't Ignore

Pet owners become remarkably familiar with toilet habits.

That familiarity is useful.

Changes in urination can provide important information about an animal's health. Cystitis, bladder infections, bladder stones and other urinary tract problems can cause pain and changes in toileting behaviour.

Possible signs of urinary problems include:

• urinating more frequently;

• straining to urinate;

• passing small amounts of urine;

• blood in the urine;

• crying or appearing uncomfortable while urinating;

• licking around the genital area;

• urinating in unusual places;

• changes in urine appearance or smell.

Cats may start visiting the litter tray repeatedly or begin urinating outside it.

That can easily be mistaken for a behavioural problem.

Sometimes it is behavioural.

Sometimes it isn't.

A cat that suddenly stops using the litter tray normally deserves attention—particularly if there are signs of straining, pain or difficulty passing urine.

Difficulty Urinating Can Be an Emergency

This point deserves emphasis.

A pet repeatedly trying to urinate but producing little or no urine needs urgent veterinary attention.

Urinary obstruction can become life-threatening.

Male cats are particularly associated with the risk of urethral obstruction, although urinary emergencies are not limited to one sex or species.

Do not wait overnight to see whether a pet who cannot pass urine improves.

12. Kidney Disease: Why Drinking More Can Matter

It is easy to think that a pet drinking plenty of water must be healthy.

Sometimes an increase in thirst is actually one of the changes owners notice when something is wrong.

The kidneys perform several essential functions, including filtering waste products and helping regulate fluid balance. Kidney disease can be acute—developing suddenly—or chronic, developing over time.

Chronic kidney disease is particularly important in older cats, although kidney problems can affect dogs too.

Potential signs can include:

• increased thirst;

• increased urination;

• reduced appetite;

• weight loss;

• vomiting;

• lethargy;

• weakness;

• changes in coat condition.

Early chronic kidney disease may not produce dramatic outward symptoms.

That is one reason routine veterinary care becomes increasingly valuable as pets age. Physical examinations and, when appropriate, blood and urine tests can sometimes identify changes that are difficult to see from behaviour alone.

Don't Restrict Water Because Your Pet Is Urinating More

If your dog or cat suddenly begins drinking and urinating more, removing access to water is not the solution.

Increased thirst may be the body's response to an underlying problem.

Pets should generally have access to fresh drinking water unless a veterinarian gives specific instructions otherwise.

Instead, monitor the change.

If possible, notice whether the increase is genuinely substantial. In multi-pet homes this can be difficult, but separate bowls or measured amounts may sometimes help you gather useful information for your vet.

13. Changes in Appetite and Weight Can Connect the Dots

By this point, several symptoms have appeared repeatedly:

weight loss

weight gain

increased thirst

frequent urination

loss of appetite

increased appetite

That repetition is useful.

Many common pet illnesses share symptoms. The body has a limited number of ways to tell us that something is wrong.

This means owners should resist searching for a perfect one-to-one relationship:

"My cat is drinking more, therefore she has kidney disease."

or:

"My dog has gained weight, therefore he has hypothyroidism."

Neither conclusion is justified by a symptom alone.

A more useful approach is:

"This is a significant change from my pet's normal behaviour. What else has changed, how long has it been happening, and should my vet investigate it?"

That shift—from trying to diagnose to trying to observe accurately—makes pet health monitoring much more useful.

14. Nutrition, Hydration and Everyday Preventative Care

Food cannot prevent every disease.

Neither can exercise.

Neither can supplements, grooming, vaccinations or regular health checks.

Preventative pet care works because several sensible habits come together.

A strong everyday routine usually includes an appropriate complete and balanced diet, access to fresh water, suitable exercise, weight management, dental care, parasite prevention, vaccinations where appropriate and routine veterinary care.

For owners interested in the broader role of nutrition and daily wellbeing, our pet health and wellness collection brings together products designed around everyday pet care and wellbeing.

But there is an important boundary between supporting health and treating disease.

A supplement does not diagnose arthritis.

A specialist food does not tell you why a cat is losing weight.

A dental product cannot repair an infected tooth.

And adding something new to a pet's routine should never delay veterinary treatment for an animal that is genuinely unwell.

Build Prevention Around the Individual Pet

Good pet healthcare changes throughout life.

A puppy's needs are not identical to those of a twelve-year-old dog. A young indoor cat and an elderly cat with chronic illness require different kinds of monitoring.

Useful preventative habits can include:

1. maintaining an appropriate body weight;

2. providing suitable daily exercise and enrichment;

3. following veterinary vaccination advice;

4. maintaining appropriate parasite control;

5. paying attention to dental health;

6. monitoring eating, drinking and toilet habits;

7. checking skin, coat, ears and body condition regularly;

8. attending routine veterinary health checks;

9. investigating persistent behaviour or physical changes;

10. adapting care as your pet ages.

There is no guarantee against illness.

There is, however, enormous value in noticing when your pet stops being their normal self.

A Note About Older Pets

Age changes the health conversation.

Senior pets may naturally sleep more, move differently and develop changing nutritional or exercise requirements. But "old age" should not become an explanation for every symptom.

Pain is not an inevitable consequence of ageing that simply has to be accepted.

Neither are substantial weight loss, extreme thirst, severe dental disease, persistent vomiting or dramatic behavioural changes.

Older pets can develop arthritis, kidney disease, thyroid conditions, diabetes, heart disease, cancer and other chronic illnesses. Some can be treated; others can be managed to improve comfort and quality of life.

The important thing is identifying what is actually happening.

Regular veterinary health checks become especially useful here because gradual changes are difficult to spot when you live with an animal every day.

Photographs and occasional weight records can help reveal changes too. Compare a photograph from today with one taken a year ago and you may suddenly notice a difference in body condition, posture or muscle mass that happened too slowly to register day by day.

From Internal Problems to Visible Warning Signs

Digestive disease, diabetes, thyroid disorders, Cushing's disease, urinary problems and kidney disease demonstrate just how much symptom overlap exists between common pet health conditions.

Increased thirst doesn't name a disease.

Weight loss doesn't name a disease.

Vomiting doesn't name a disease.

They tell you that something may need investigating.

And not every important warning sign comes from inside the digestive, urinary or endocrine systems.

Some are much easier to see—or hear.

A red eye. A dog repeatedly shaking its head. A cat suddenly losing its balance. An unexplained lump. A persistent cough. A seizure. Difficulty breathing.

15. Ear Infections: When Head-Shaking Means More Than an Itch

A quick shake of the head after a bath is one thing.

Repeated head-shaking, scratching and obvious discomfort are another.

Ear infections are among the problems dog owners in particular may encounter, although cats can develop ear disease too. The underlying cause is not always obvious. Bacteria and yeast may be involved, while allergies, parasites, foreign material and other conditions can contribute to ear problems.

Signs worth watching for include:

• frequent head-shaking;

• scratching at one or both ears;

• redness or swelling;

• discharge;

• an unpleasant smell;

• sensitivity when the ear is touched;

• holding the head unusually;

• visible irritation;

• apparent pain.

Persistent ear problems need veterinary attention.

Simply cleaning an inflamed ear repeatedly without knowing what is causing the problem can make matters worse, particularly if the ear is painful or damaged.

What Is an Ear Haematoma?

Repeated vigorous head-shaking or scratching can sometimes contribute to an aural haematoma, where blood accumulates within the ear flap.

The ear may suddenly look thick, swollen or balloon-like.

This is another situation for veterinary assessment rather than attempting to drain or treat the swelling at home.

And there is a broader lesson here.

When a pet repeatedly scratches, shakes, licks or rubs one particular area, don't focus only on stopping the behaviour.

Ask why they are doing it.

16. Eye Problems: Redness, Discharge and Changes in Vision

Eyes can change quickly, and certain eye problems can be painful.

Common conditions owners may encounter include conjunctivitis, cataracts, glaucoma, dry eye and corneal ulcers. These conditions have different causes and treatments, despite sometimes producing superficially similar symptoms.

Warning signs include:

• redness;

• excessive watering;

• unusual discharge;

• squinting;

• keeping an eye closed;

• rubbing or pawing at the face;

• cloudiness;

• swelling;

• sensitivity to light;

• a visible injury;

• apparent changes in vision.

A red eye is not a diagnosis.

Neither is eye discharge.

Because some eye conditions can threaten vision and may worsen rapidly, painful, injured, cloudy or suddenly abnormal eyes deserve prompt professional attention.

Never put leftover human or animal eye medication into your pet's eye unless a veterinary professional has specifically told you to use that medication for the current problem.

The wrong treatment may be ineffective and, in some circumstances, inappropriate for the condition present.

17. Epilepsy, Seizures and Neurological Problems

Few pet symptoms are more frightening to witness than a seizure.

A seizure can involve collapsing, involuntary movements, stiffening, paddling of the limbs or altered awareness. Some animals may behave strangely before or after an episode.

Epilepsy is one possible cause of recurrent seizures, but a seizure does not automatically mean a pet has epilepsy.

Seizures can have different underlying causes, which is why veterinary investigation matters.

If your pet has a seizure:

1. move hazards away where this can be done safely;

2. keep the surrounding environment calm;

3. do not restrain your pet unnecessarily;

4. keep your hands away from their mouth;

5. time the episode if possible;

6. contact a veterinary professional for advice.

Contrary to a persistent myth, do not put your hand or an object into a seizing animal's mouth.

If it is safe to do so, recording a video can sometimes provide useful information for your vet because the episode may have ended before your pet reaches the clinic.

Prolonged seizures, repeated seizures close together, failure to recover normally or a first-time seizure require particularly prompt veterinary advice.

Neurological Signs Aren't Limited to Seizures

Other potential neurological symptoms can include:

• tremors;

• loss of balance;

• unusual weakness;

• disorientation;

• circling;

• abnormal movements;

• changes in coordination;

• sudden behavioural changes.

These symptoms can have numerous causes.

Sudden neurological changes should not be diagnosed from an online symptom list.

18. Coughing, Breathing Problems and Respiratory Disease

Pets cough for different reasons.

Respiratory infections are one possibility. Heart problems are another. Irritation, inflammation and other diseases can also affect breathing.

Among the respiratory and infectious conditions owners may hear about are kennel cough, canine influenza, bronchitis, pneumonia and other viral or bacterial infections.

Possible respiratory symptoms include:

• coughing;

• sneezing;

• nasal discharge;

• noisy breathing;

• reduced exercise tolerance;

• lethargy;

• changes in appetite;

• faster or more difficult breathing.

A mild cough and difficulty breathing belong in very different categories.

Breathing problems can be an emergency.

If your pet is struggling for breath, breathing with obvious effort, collapses or develops concerning changes in gum colour, seek urgent veterinary help rather than trying home remedies first.

Kennel Cough Isn't Only About Kennels

The term "kennel cough" can be misleading.

Dogs do not need to live in a kennel to develop infectious respiratory disease. Close contact with other dogs can occur in numerous environments.

If your dog develops a persistent cough—particularly after spending time around other dogs—contact your vet for advice and mention the cough before entering a waiting room. The clinic may want to take precautions to reduce potential exposure to other animals.

Vaccination can form part of preventative healthcare for certain infectious diseases. Your veterinary practice can recommend an appropriate vaccination programme based on your pet's age, health, lifestyle and individual risk.

19. Heart Disease: Subtle Signs Can Matter

Heart disease is not one single condition.

Different diseases can affect the heart's structure or function, and the symptoms can vary depending on the animal and the particular problem involved.

Possible warning signs can include:

• coughing;

• reduced stamina;

• reluctance to exercise;

• weakness;

• faster breathing;

• difficulty breathing;

• collapse;

• changes in body weight;

• a swollen abdomen.

The frustrating part?

Several of those symptoms overlap with respiratory disease, obesity, arthritis and other pet health problems.

A dog slowing down on walks could have painful joints.

Or a heart problem.

Or a respiratory problem.

Or something else entirely.

This is why exercise intolerance deserves more thought than simply assuming an animal has become lazy.

Veterinary examination may involve listening to the heart and lungs, followed by further tests where indicated.

Congestive heart failure can occur when heart disease progresses to the point where the heart cannot meet the body's needs effectively and fluid accumulation may occur. It requires veterinary diagnosis and management.

20. Lumps, Bumps and Cancer

Finding a lump on your pet is unsettling.

The mind tends to leap immediately to one word:

Cancer.

But not every lump is cancerous.

Pets can develop different types of masses, including benign growths such as some lipomas. Other lumps may be inflammatory, infectious or malignant.

Unfortunately, appearance and touch alone cannot reliably tell you what every lump is.

A soft lump is not automatically harmless.

A firm lump is not automatically cancer.

And a lump that doesn't appear to bother your pet may still deserve examination.

Use the "New or Changing" Rule

Have new lumps checked and monitor existing ones according to veterinary advice.

Changes worth reporting include:

• increasing size;

• altered shape;

• changes in colour;

• bleeding;

• ulceration;

• discharge;

• becoming painful;

• suddenly growing faster;

• interfering with movement, eating or other normal activities.

Taking a photograph beside a ruler can help document visible changes between appointments.

Your vet may recommend taking a sample from a lump to learn more about the cells involved. The appropriate approach depends on the individual mass.

Cancer Can Cause More Than Lumps

Cancer does not always appear as something you can feel beneath the skin.

Depending on the type and location, potential signs may include unexplained weight loss, appetite changes, persistent lethargy, abnormal bleeding, swelling, coughing or changes in normal bodily functions.

Those symptoms are not specific to cancer.

They are reasons to investigate, not reasons to assume the worst.

21. Poisoning: Everyday Items Can Become Pet Emergencies

Pets investigate the world with enthusiasm and questionable judgement.

Dogs in particular have a talent for finding the one thing in a room they absolutely should not eat.

Potential hazards can include foods, medicines, household chemicals, plants and other substances.

Examples owners commonly need to be aware of include chocolate, grapes and raisins, although this is far from a complete list of potential toxins.

If you think your pet has swallowed something harmful:

do not wait for symptoms before seeking professional advice.

Knowing exactly what was consumed, approximately how much, when it happened and your pet's approximate weight can help a veterinary professional assess the situation.

Keep packaging where possible.

Do not automatically make your pet vomit. Whether vomiting is appropriate depends on the substance and circumstances, and attempting to induce it incorrectly can create additional danger.

For a broader look at preparing for unexpected situations, our essential pet first aid guide covers practical first-response principles owners should understand before an emergency happens.

Suspected poisoning is a "call now" problem, not a "search the internet for an hour" problem.

22. Heatstroke: Prevention Matters

Pets cannot manage heat exactly as humans do.

Dogs primarily lose heat through panting, with additional heat loss through other mechanisms, and they can become dangerously overheated in unsuitable conditions. Certain animals may be particularly vulnerable because of age, health, body condition or physical characteristics.

Warning signs associated with overheating can include:

• excessive panting;

• distress;

• drooling;

• weakness;

• confusion;

• vomiting or diarrhoea;

• collapse.

Heatstroke can become life-threatening.

Prevention means thinking beyond simply avoiding hot cars.

Exercise intensity, direct sunshine, humidity, access to shade and water, hot surfaces and the individual animal's ability to cope with heat all matter.

On warm days, adapt activity to the conditions and the pet in front of you.

The walk can wait.

23. Wounds and Injuries: Small Doesn't Always Mean Minor

Cuts, bites, torn nails and other injuries are part of life with active animals.

Some are obvious.

Others hide beneath fur.

Bite wounds are particularly deceptive because a small puncture at the surface can conceal deeper tissue damage and infection.

Check an injured pet carefully without putting yourself at risk. Even an exceptionally gentle animal may bite when frightened or in pain.

Veterinary attention may be needed for:

• deep wounds;

• heavy or persistent bleeding;

• bite injuries;

• contaminated wounds;

• injuries involving the eye;

• severe limping;

• suspected fractures;

• substantial swelling;

• wounds that become red, painful or discharge fluid;

• injuries accompanied by weakness or collapse.

Avoid giving human painkillers unless a vet has specifically instructed you to do so.

Human medication is not automatically safe for dogs or cats.

24. Pyometra and Reproductive Emergencies

Owners of unspayed female dogs and cats should be aware of pyometra, a serious infection of the uterus.

It can become life-threatening and requires veterinary treatment.

Potential signs can include:

• lethargy;

• reduced appetite;

• increased thirst;

• increased urination;

• vomiting;

• abdominal swelling;

• vaginal discharge in some cases.

Importantly, discharge may not always be present.

This is another example of why combinations of vague symptoms should not simply be ignored. Increased thirst plus lethargy could have several explanations; reproductive status and recent history can provide important additional clues.

If an unspayed female becomes unwell—particularly in the weeks following a season—contact a veterinary professional promptly.

25. Changes in Behaviour Can Be Health Symptoms Too

Not every pet symptom is physical.

Sometimes the first sign of pain or illness is a change in personality.

A sociable cat starts hiding.

A tolerant dog suddenly growls when touched.

An older animal becomes restless at night.

A previously house-trained pet begins having accidents indoors.

A dog that adored walks starts hiding when the lead appears.

Behaviour changes can certainly have behavioural or environmental causes, but physical discomfort and illness should also be considered.

Watch for:

• increased irritability;

• withdrawal;

• hiding;

• restlessness;

• altered sleep;

• reduced interest in play;

• sudden sensitivity to touch;

• house-soiling;

• changes in interaction with people or other pets;

• confusion or disorientation.

The more sudden or dramatic the change, the more important it becomes to consider an underlying health problem.

This is especially relevant in older animals.

Do not assume a senior pet has suddenly become "grumpy."

They may hurt.

26. When Should You Take Your Pet to the Vet?

This is the question owners ultimately want answered.

And the answer depends on what is happening, how severe it is, how long it has lasted and the individual animal involved.

Some mild symptoms can be monitored.

Others justify making a routine appointment.

Some require urgent or emergency veterinary care.

Contact a Vet Promptly If You Notice Persistent Changes Such As:

• repeated vomiting or diarrhoea;

• unexplained weight loss;

• substantial appetite changes;

• increased thirst or urination;

• persistent coughing;

• recurrent skin problems;

• ongoing limping or stiffness;

• persistent bad breath or apparent dental pain;

• new or changing lumps;

• recurrent ear problems;

• changes in urination;

• unusual lethargy;

• significant behaviour changes.

You do not need to know what disease is causing the symptom before calling.

That is what veterinary investigation is for.

Seek Urgent Veterinary Help for Potential Emergencies

Examples include:

• difficulty breathing;

• collapse;

• severe weakness;

• prolonged or repeated seizures;

• inability to urinate;

• severe or uncontrolled bleeding;

• suspected poisoning;

• major trauma;

• severe abdominal swelling or distress;

• serious eye injuries;

• extreme overheating or suspected heatstroke;

• rapidly deteriorating symptoms.

This is not an exhaustive emergency list.

If your instincts tell you something is seriously wrong, contact your veterinary practice or emergency veterinary service and describe exactly what is happening.

27. Preventative Pet Care: The Habits That Matter

After reading about pet diseases, infections, diabetes, arthritis, kidney problems and emergencies, it is easy to feel as though danger is waiting around every corner.

That is not the point of knowing about common pet health problems.

The point is to become observant, prepared and proactive.

Preventive healthcare does not guarantee that an animal will never become ill. It creates opportunities to support wellbeing and identify potential problems earlier.

A sensible routine can include:

1. Regular veterinary check-ups appropriate for your pet's age and health.

2. Vaccinations based on veterinary recommendations and individual risk.

3. Parasite control appropriate to lifestyle and exposure.

4. Dental care and regular attention to teeth and gums.

5. A complete, balanced diet appropriate to species and life stage.

6. Healthy weight management rather than relying on appearance alone.

7. Regular exercise suited to age, breed, health and mobility.

8. Grooming and body checks to spot skin problems, parasites, wounds and lumps.

9. Monitoring eating, drinking and toilet habits.

10. Taking persistent changes seriously.

Everyday enrichment matters as well.

Mental stimulation, play and appropriate activity are part of an animal's overall quality of life. Owners looking to build more variety into their dog's routine can explore our dog toys collection, while our cat toys collection offers options for play and engagement for feline family members.

Exercise should, of course, match the individual animal.

More is not automatically better.

A young, energetic dog and an older dog with osteoarthritis need very different routines.

28. Keep a Simple Pet Health Checklist

You do not need spreadsheets, colour-coded folders or a veterinary textbook.

A straightforward monthly mental check can be enough to make you more aware of gradual changes.

Ask yourself:

The value is in comparison.

You are not asking whether your pet matches somebody else's definition of normal.

You are asking:

"Is this normal for my pet?"

29. What You Should Never Do When Your Pet Seems Unwell

Knowing what not to do is part of responsible pet healthcare too.

Avoid:

• giving human medication without veterinary instruction;

• using another pet's prescription medication;

• repeatedly treating symptoms without investigating why they return;

• delaying emergency care while searching for home remedies;

• assuming persistent pain is simply old age;

• forcing food or water into a seriously unwell animal;

• inducing vomiting after suspected poisoning unless specifically instructed;

• using dog medication on a cat, or vice versa, without professional confirmation;

• ignoring sudden behavioural changes;

• assuming that because your pet is eating, they cannot be seriously unwell.

The internet is useful for education.

It is much less useful for diagnosing an individual animal.

Two pets can display remarkably similar symptoms while having entirely different underlying conditions.

30. Early Detection Starts With Knowing Your Pet

After all the medical terminology—arthritis, dermatitis, periodontal disease, diabetes, hyperthyroidism, hypothyroidism, cystitis, kidney disease, epilepsy, respiratory infections—the most useful skill for an owner remains remarkably simple.

Know your animal.

Know how they normally walk.

Know how eagerly they normally eat.

Know roughly how much they drink.

Know their usual toilet habits.

Know whether they leap onto the bed or ask to be lifted.

Know how their coat normally feels, what their eyes normally look like and how they usually behave when they are comfortable.

Then pay attention when the pattern changes.

Early detection does not mean identifying the disease yourself.

It means noticing the clue.

Common Pet Health Problems Every Owner Should Know: Final Takeaways

Pets cannot tell us, "My tooth has been hurting for three weeks," or "I've started feeling unusually thirsty."

They communicate differently.

A limp.

An untouched breakfast.

An empty water bowl.

A strange cough in the night.

A cat who suddenly stops jumping onto the windowsill.

A dog who scratches until the skin becomes red.

Small observations can become important information.

The most common pet illnesses and health conditions cover almost every system in the body, but owners do not need to memorise an encyclopaedia of veterinary medicine.

Remember the principles instead:

• Know what is normal for your pet.

• Watch for persistent or unexplained changes.

• Look at combinations of symptoms rather than one sign in isolation.

• Maintain sensible preventative healthcare.

• Do not self-diagnose from symptoms alone.

• Seek veterinary advice when a problem persists, causes pain or concerns you.

• Treat breathing difficulties, collapse, inability to urinate, major trauma, poisoning and other serious symptoms as potential emergencies.

Your role as an owner is not to diagnose diabetes, distinguish arthritis from hip dysplasia or decide whether a lump is malignant.

Your role is to notice.

Veterinary professionals can take it from there.

Ultimately, good pet healthcare is not about worrying constantly that something might go wrong. It is about giving your dog or cat the everyday care they need, recognising meaningful changes and knowing when professional help is the right next step.

Because sometimes the most important sign of illness is not dramatic at all.

Sometimes it is simply:

"That's not like them."

And knowing your pet well enough to notice the difference can be one of the most valuable health tools you have.

Frequently Asked Questions About Common Pet Health Problems

1. What are the most common health problems in dogs and cats?

Dogs and cats can experience many of the same broad health concerns, including skin problems, allergies, dental disease, digestive problems, obesity, parasites, arthritis, ear infections, urinary problems and kidney disease. Diabetes and heart disease can affect both species too.

However, the likelihood of particular conditions varies according to species, breed, genetics, age, lifestyle and existing health. Cats and dogs can also show illness differently, so knowing what is normal for your individual pet is particularly important.

2. Do certain dog and cat breeds have more health problems than others?

Yes. Genetics and physical characteristics can make some breeds more predisposed to particular pet health conditions.

For example, inherited factors can contribute to certain joint, eye, heart and other disorders. Body shape can matter too. However, having a genetic predisposition does not mean an individual animal will definitely develop that disease.

If you own a particular breed, ask your vet which health problems are worth monitoring throughout that animal's life.

3. How often should a healthy pet have a veterinary check-up?

There isn't one schedule suitable for every animal. Age, species, breed, lifestyle, existing medical conditions and medication can all affect how frequently veterinary health checks are appropriate.

A healthy young adult may have very different requirements from a puppy or kitten, a senior pet, or an animal living with chronic illness.

Your veterinary practice can recommend an examination and preventative healthcare schedule appropriate for your individual pet.

4. Can indoor pets still develop common diseases and parasites?

Absolutely.

Living indoors may reduce exposure to certain hazards, but it does not make an animal immune to disease. Indoor pets can still develop dental disease, obesity, diabetes, arthritis, kidney disease, urinary problems, heart disease, cancer and other health conditions.

Parasite risk may also still exist depending on the animal's circumstances and household. Rather than assuming an indoor pet needs no parasite protection, discuss their individual risk with your vet.

5. Can stress cause physical health problems in pets?

Stress can affect an animal's behaviour and physical wellbeing.

Possible signs associated with stress can include changes in appetite, hiding, restlessness, altered toileting behaviour, excessive grooming or changes in interaction.

The complication is that many of these behaviours can also occur with physical illness.

A cat hiding more often, for example, could be stressed—but could also be experiencing pain. Persistent or unexplained behavioural changes therefore deserve investigation rather than automatically being labelled as anxiety or stress.

6. Why does my pet keep getting the same health problem?

Recurring symptoms can happen for numerous reasons.

The original problem may not have fully resolved, an underlying trigger may still be present, or the pet could have a chronic condition requiring longer-term management. Recurrent skin inflammation, digestive problems, urinary symptoms and ear infections are good examples of problems where identifying the underlying cause can be important.

If a condition repeatedly returns, tell your vet how often it happens and what treatment has previously been used. A simple written symptom history can be extremely useful.

7. Are human illnesses contagious to pets?

Some infectious diseases can pass between humans and animals, although many everyday human illnesses will not affect pets in the same way.

Diseases capable of spreading naturally between animals and humans are known as zoonotic diseases. Transmission can potentially occur in either direction depending on the particular disease.

Good hygiene, appropriate parasite control, responsible handling of animal waste and veterinary preventative care can help reduce certain risks. If someone in your household has a diagnosed infectious disease and you are concerned about your pet, ask your vet or doctor for advice specific to that infection.

8. Should I get a second veterinary opinion about my pet's health?

Seeking a second veterinary opinion can be reasonable when you want another professional perspective on a diagnosis, treatment plan or complicated ongoing condition.

It may be particularly useful when a condition is unusual, symptoms remain unexplained or specialist expertise is required.

Bring or arrange access to relevant medical records, test results, imaging and medication information where possible. This helps the second veterinarian understand what has already been investigated and avoids unnecessary repetition.

9. What health information should I keep for my pet?

Keeping basic health records can make veterinary appointments and emergencies much easier.

Useful information includes your pet's vaccination history, current medications, known allergies or adverse reactions, previous illnesses, operations, ongoing health conditions and veterinary contact details. Keeping an occasional weight record can also help reveal gradual changes that are difficult to notice day to day.

If your pet takes regular medication, keep the exact medication name, strength and dosage recorded somewhere accessible.

10. What should I tell my vet when my pet is sick?

Give your vet specific observations rather than trying to provide your own diagnosis.

Useful information includes:

• when the problem started;

• whether symptoms appeared suddenly or gradually;

• how frequently they occur;

• changes in appetite or drinking;

• vomiting or diarrhoea;

• changes in urination or bowel movements;

• weight changes;

• coughing or breathing changes;

• changes in movement or behaviour;

• current medication and supplements;

• anything unusual your pet may have eaten or encountered.

Photos or videos can also be helpful for intermittent symptoms such as unusual movements, coughing episodes, limping or behavioural changes.

Most importantly, don't worry about using medical terminology. "My dog normally races upstairs but has refused to climb them since yesterday" can be more useful to a vet than trying to decide whether your dog has arthritis yourself.

The goal is simple: describe what changed, when it changed and what has happened since.