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Cat Health Warning Signs: 15 Symptoms You Must Not Ignore

By Rachel, Cat Care Specialist · Updated 2026-04-21

Cats have an extraordinary talent for hiding illness until it becomes impossible to conceal. This is not stubbornness or independence — it is a hardwired survival instinct that dates back to their wild ancestors. A cat that shows obvious weakness in the wild becomes a target, so the species evolved to conceal pain and discomfort until conditions are severe. For cat owners, this means the responsibility falls on us to know what subtle — and not-so-subtle — warning signs mean. Recognising these fifteen symptoms, and acting quickly on them, is one of the most powerful things you can do to protect your cat's health and potentially save their life.

Table of Contents

Why Cats Hide Illness: The Survival Instinct

Understanding why cats hide illness makes it easier to spot the signs. In nature, a predator is always looking for weakness in prey. By hiding discomfort, cats avoid appearing vulnerable. This instinct persists strongly in domestic cats, even those who have never faced a predator and live in comfortable homes.

What this means in practice is that obvious symptoms in a cat often mean the disease or condition is already advanced. The mild limp you notice today may be the only visible sign of significant pain your cat has been experiencing for weeks. The extra hour of sleep your cat is getting might be lethargy from an infection that started days ago.

This is why so much of feline health monitoring is about pattern recognition. You need to know what is normal for your cat so that deviations from normal — however subtle — trigger concern. A cat that suddenly starts sleeping in the back of the cupboard when they normally sleep on your bed is showing a warning sign, even if they appear otherwise normal.

The 15 Warning Signs

1. Sudden Hiding or Withdrawal

A cat that suddenly hides in unusual places — under beds, inside wardrobes, in dark corners — when they normally seek out company or their usual resting spots is telling you something is wrong. This is one of the most reliable early indicators of pain or illness in cats. It is also one of the most frequently ignored, because cats do sometimes change their resting spots based on temperature or noise.

The difference is degree and context. A cat that has never hidden under the bed and suddenly cannot be coaxed out is showing a significant change. A cat that retreats briefly during a thunderstorm and returns when it passes is normal. Know your cat's baseline so you can identify deviations.

Hiding is not a diagnosis — it tells you something is wrong, not what is wrong. The cause could range from pain to infection to stress. A veterinary visit is the appropriate response to sudden, unexplained hiding.

Cat hiding under furniture in a dark corner

2. Changes in Eating or Drinking

Cats are creatures of habit with strong food preferences, and any change in eating or drinking behaviour is a potential warning sign. This includes eating significantly less than usual, refusing favourite foods entirely, eating more than usual (which can indicate hyperthyroidism or diabetes), drinking far more water than normal, or not drinking at all.

A cat that stops eating entirely for more than 24 hours is at serious risk of hepatic lipidosis, a life-threatening liver condition that develops when cats do not eat. This is not an exaggeration — cats literally can develop fatal liver disease from fasting. Never assume a cat not eating is simply being fussy.

Increased thirst is equally concerning because it is a classic symptom of several serious conditions: chronic kidney disease, diabetes mellitus, and hyperthyroidism. All three are manageable with early veterinary intervention. A cat drinking noticeably more water than usual should have basic blood work and urinalysis to screen for these conditions.

Two water bowls showing increased water consumption

3. Weight Loss Without Explanation

Unexplained weight loss in cats is always significant, even when your cat appears to be eating normally. Weight loss occurs when the body is burning more calories than it is consuming — a sign that something is wrong at a metabolic level. Causes include hyperthyroidism, diabetes, kidney disease, intestinal parasites, inflammatory bowel disease, and certain cancers.

Weigh your cat monthly. A kitchen scale is accurate enough for this purpose. Keep a log. If your cat loses more than 5% of their body weight over a month without a clear explanation (such as a recent diet change), see your veterinarian. Weight loss is particularly concerning in older cats, where thyroid disease and kidney problems are common causes.

You may not be able to see weight loss visually until it is quite advanced. Regularly running your hands along your cat's ribs and spine gives you a tactile sense of their body condition. A cat that feels bonier than usual — with more prominent ribs and spine — is likely losing weight.

4. Lethargy and Decreased Activity

All cats sleep a lot — between 12 and 16 hours per day is normal. The concern is when a cat that normally plays, jumps, climbs, and interacts becomes significantly less active. A cat that stops jumping onto their favourite perch, stops greeting you at the door, sleeps in unusual positions, or seems reluctant to move may be in pain or unwell.

The distinction between normal cat laziness and concerning lethargy lies in the complete picture. A normal lazy cat will still respond to stimulus — a noise, a treat, an invitation to play. A lethargic cat is not responding normally and may be subdued even in situations where they previously engaged.

Lethargy accompanies virtually every significant illness in cats, from infections to organ disease to cancer. On its own it is not diagnostic, but combined with any other warning sign it points strongly toward needing veterinary attention.

5. Changes in Litter Box Habits

Changes in litter box habits are among the most meaningful warning signs in cats because they are easy to observe and often indicate significant internal issues.

Straining to urinate or defecate is always a concern. Straining to urinate in a male cat is a potential emergency (see Sign 6). Straining to defecate can indicate constipation, intestinal obstruction, or pain in the spine or pelvis. Both warrant veterinary assessment.

Urinating significantly more or less than usual, urinating outside the box, urine that is bloody or unusually dark, and faeces that are very hard and dry or very loose and watery are all worth investigating. Changes in litter box habits are frequently the first sign of kidney disease, diabetes, hyperthyroidism, and urinary tract conditions.

Litter box showing changes in urine output

6. Straining to Urinate (Especially in Male Cats)

This deserves its own section because it is one of the most urgent feline emergencies. Male cats have a narrow urethra that can become blocked by crystals, stones, or a plug of cells and mucus. When a blockage occurs, the cat cannot urinate, urine backs up into the bladder and kidneys, and without treatment, the cat dies from kidney failure or a ruptured bladder within 24 to 48 hours.

Signs of a urinary blockage include straining to urinate with little or no urine produced, crying or vocalising while straining, frequent trips to the litter box, licking the genital area excessively, and behaviour that appears agitated or restless. A male cat that is straining and producing no urine should be treated as an emergency immediately — even if it is 3am, even on a weekend.

Female cats can also develop urinary issues, including infections and cystitis, and while their wider urethra makes complete blockage less common, straining to urinate in any cat should be evaluated promptly.

7. Vomiting or Diarrhea That Persists

Occasional vomiting — particularly a hairball — is normal in cats. Frequent or persistent vomiting is not. Vomiting more than twice in a day, vomiting that continues over several days, vomiting that contains blood, or vomiting accompanied by lethargy or loss of appetite are all warning signs requiring veterinary assessment.

Diarrhea similarly ranges from a brief, self-resolving problem to a symptom of serious disease. Diarrhea that is bloody, black (which indicates digested blood in the upper gastrointestinal tract), watery and explosive, or persistent for more than 48 hours requires veterinary investigation. Kittens, senior cats, and cats with compromised immune systems are particularly vulnerable to dehydration from diarrhea and need prompt care.

See our article on why cats vomit for a detailed breakdown of causes and when to worry.

8. Difficulty Breathing or Open-Mouth Breathing

Cats normally breathe quietly and effortlessly with a closed mouth. Any visible difficulty breathing — laboured chest movement, flared nostrils, extended neck, audible breathing — is a medical emergency that requires immediate veterinary care. Open-mouth breathing in a cat is not normal under any circumstances and should be treated as an emergency even before reaching the vet.

Blue or pale gums alongside breathing difficulty indicate poor oxygenation and requires the highest level of urgency. Pink gums with slightly faster breathing might wait until normal clinic hours. Blue gums do not.

Rapid breathing at rest (above 40 breaths per minute) is also concerning. Count your cat's breathing rate when they are sleeping peacefully. A normal rate is 20 to 30 breaths per minute. Sustained rates above 40, even without obvious distress, warrant veterinary evaluation.

Breathing problems in cats can stem from asthma, heart disease, fluid in the chest, infections, trauma, and toxin exposure. None of these improve without treatment.

Cat breathing laboured with visible chest movement

9. Limping or Reluctance to Move

Limping is obvious, but cats often show reluctance to move in subtler ways that owners mistake for normal laziness. Watch for your cat not jumping up to places they previously reached easily, avoiding stairs, sliding when trying to get up from a resting position, or favouring one leg consistently when walking.

Causes range from arthritis (common in senior cats and often undiagnosed) to injuries, infections, and bone disease. Even a cat that seems to have recovered from a fall needs to be examined — some injuries have delayed symptoms and internal damage that worsens without treatment.

Arthritis deserves special mention because it is dramatically underdiagnosed in cats. Studies suggest that over 60% of cats over the age of six have some degree of arthritis, yet most owners and many veterinarians miss it because cats hide their pain so effectively. If your senior cat has become less active, less willing to jump, or seems stiffer after rest, mention arthritis as a possibility to your vet.

10. Changes in Vocalisation

A normally quiet cat that suddenly becomes very vocal, or a chatty cat that goes silent, is showing a warning sign. Changes in vocalisation can indicate pain (crying or yowling during movement or when picked up), hyperthyroidism (increased vocalisation, particularly at night), high blood pressure (vocalising in confusion or distress), and cognitive dysfunction in senior cats (vocalising more at night, often seeming disoriented).

The context matters. A cat that yowls when straining to urinate is showing pain. A cat that yowls at an empty room and seems confused is showing possible cognitive decline or high blood pressure. A cat that has always been chatty and continues to be chatty in the same contexts is probably fine. A change in pattern is what you are looking for.

11. Coat Deterioration

A cat's coat is one of the most visible indicators of their internal health. A healthy cat grooms regularly and maintains a glossy, smooth coat. Coat deterioration — a dull, greasy, matted, or patchy coat — indicates that something is interfering with normal grooming, nutrition absorption, or skin health.

Possible causes include pain (a cat in pain stops grooming because grooming is physically uncomfortable), dental disease (pain makes grooming unpleasant), hyperthyroidism, kidney disease, diabetes, parasites, allergies, and skin infections. A cat with a sudden coat change needs veterinary investigation.

Areas of hair loss — not just matting but actual bald patches — warrant prompt attention. Potential causes include allergies, ringworm, parasites, hormonal imbalances, and stress-related over-grooming.

12. Eye or Nasal Discharge

Discharge from the eyes or nose is a sign of respiratory infection, allergies, or more serious conditions like feline herpesvirus or calicivirus. Clear, watery discharge may indicate allergies or a mild viral infection. Thick, yellow or green discharge indicates bacterial infection. Blood-tinged discharge requires immediate veterinary attention.

Eye discharge accompanied by squinting, cloudiness, or a visible third eyelid is particularly concerning, as it can indicate an eye ulcer, glaucoma, or systemic illness. Eye problems in cats can deteriorate rapidly and may threaten vision, making prompt treatment essential.

Nasal discharge combined with lethargy, loss of appetite, and laboured breathing can indicate a serious upper respiratory infection that requires antibiotics and supportive care.

Cat showing eye discharge requiring veterinary attention

13. Pale or Blue Gums

Lift your cat's lip and look at their gums. They should be pink. Pale pink or white gums indicate anaemia or poor circulation — both serious. Yellow gums indicate jaundice, which points to liver disease or severe haemolysis. Blue or purple gums indicate a lack of oxygen, meaning a breathing or cardiovascular emergency.

Check your cat's gum colour monthly as part of a home health check. Learn what your individual cat's normal gum colour looks like so you can detect changes. Gums should be pink, moist, and return to pink within 2 seconds of being pressed gently with a finger.

Gum colour changes are not something to monitor at home over days. If your cat's gums are pale, blue, or yellow, seek veterinary care immediately.

14. Seizures or Collapse

A cat that has a seizure or collapses without explanation requires immediate emergency veterinary care. Seizures in cats can result from epilepsy, toxin ingestion, brain tumours, low blood sugar, liver disease, or severe infection. Whatever the cause, a seizing cat needs veterinary assessment urgently.

During a seizure: do not put your hands near the cat's mouth (they may bite involuntarily), remove objects from around them that could cause injury, time the seizure (seizures lasting more than five minutes are particularly dangerous), and contact your vet or emergency clinic immediately.

A cat that collapses — meaning they fall over and cannot get up — may be experiencing heart failure, severe anaemia, internal bleeding, or a metabolic crisis. Treat this as an absolute emergency.

15. Swollen or Painful Abdomen

A swollen or distended abdomen in a cat is never normal and requires prompt veterinary assessment. Possible causes include fluid accumulation (ascites), an enlarged organ from heart failure or liver disease, intestinal obstruction, a ruptured bladder, pregnancy (if an intact female), and cancer. A bloated, hard abdomen accompanied by crying, lethargy, or vomiting is an emergency.

Visible distension is not always present — sometimes the abdomen is simply painful to touch. If your cat resists being picked up, shows discomfort when you touch their belly area, or has a hunched posture (indicating abdominal pain), these all warrant veterinary assessment.

Pain in the abdominal area combined with straining to urinate, vomit, or not eating elevates the urgency significantly. Kidney stones, intestinal blockages, and organ torsion are all conditions that require urgent surgical intervention.

Building a Home Health Check Routine

Performing a basic monthly health check at home takes under five minutes and can catch problems before they become serious.

Eyes: Clear, bright, no discharge. Third eyelid should not be persistently visible.

Nose: No discharge, no bleeding, no crusting.

Mouth and gums: Pink gums, no sores, no bad breath beyond normal.

Body condition: Run your hands along the ribs and spine — you should feel a thin fat layer but the bones should not be prominently visible. Weigh monthly.

Coat: Smooth and glossy, no bare patches, no mats.

Behaviour: Normal energy, normal appetite, normal litter box habits. Note any changes from the previous month.

Breathing: Count breaths while sleeping. 20–30 breaths per minute is normal. Note any laboured breathing.

Establish a baseline. What is normal for your cat may differ from what is normal for someone else's cat. When you know the baseline, changes become obvious.

When in Doubt: See the Vet

Trust your instincts. If something about your cat seems wrong to you — even if you cannot identify exactly what it is — it is worth a veterinary visit. Cats are very good at appearing normal even when they are not. A small investment in a check-up can catch something that would otherwise become a serious, expensive, or fatal problem.

The general principle: it is better to see the vet and find nothing wrong than to delay and find a serious condition too late.

Annual veterinary check-ups are the minimum for adult cats. Senior cats over ten years old should ideally be examined twice yearly, as many conditions become more common with age and early detection matters more.

Frequently Asked Questions {#frequently-asked-questions)

Why do cats hide when they are ill?

Hiding is a survival instinct. Wild cats hide weakness to avoid appearing vulnerable to predators. This instinct persists in domestic cats, meaning obvious illness symptoms in cats often appear only when conditions are advanced. This is why regular home monitoring and prompt veterinary response to subtle changes is critical.

Is my cat just being lazy or could lethargy be a health problem?

A cat sleeping more than normal, avoiding jumping, moving reluctantly, and withdrawing from interaction when they previously engaged normally is showing a warning sign. Normal lazy behaviour still includes periods of activity and engagement. A sustained change in energy level warrants veterinary evaluation.

My male cat is straining to urinate but producing very little. Is this an emergency?

Yes, immediately. Male cats straining to urinate with little or no output may have a urinary blockage, which is fatal within 24–48 hours without treatment. This is one of the most urgent feline emergencies. See a veterinarian right away.

What causes rapid breathing in cats and when is it an emergency?

Normal cat breathing is 20–30 breaths per minute at rest with a closed mouth. Rapid breathing above 40 breaths per minute, open-mouth breathing, blue or pale gums, or laboured breathing all require immediate veterinary attention.

What should I do if my cat stops eating for more than 24 hours?

A cat not eating for more than 24 hours is at risk of hepatic lipidosis, a serious and potentially fatal liver disease. Seek veterinary care promptly. Do not wait to see if the cat eats later.

Can constipation be a sign of serious illness in cats?

Yes. Chronic constipation can indicate megacolon, kidney disease, dehydration, or intestinal obstruction. Straining in the litter box should always be evaluated by a vet to determine the cause.

Is blood in my cat's urine an emergency?

Yes. Blood in cat urine requires veterinary evaluation to determine the cause — possible causes include urinary tract infection, bladder stones, trauma, and in some cases cancer. Prompt attention is essential.

Why is my cat drinking far more water than usual?

Increased thirst can indicate kidney disease, diabetes, hyperthyroidism, or liver disease. All are manageable with early veterinary intervention. A cat drinking noticeably more water than usual should have blood work and urinalysis done.

Sources

Rachel is a cat care specialist with a background in veterinary nursing and over a decade of experience writing about feline health, behaviour, and nutrition. She has seen too many preventable feline health crises escalate because owners did not know what warning signs to watch for. She writes to change that.

Last updated: April 2026