How to Tell If Your Cat Is Sick: 10 Signs Owners Often Miss

Cats are the masters of masking illness. By the time a cat seems obviously unwell, the condition may have been developing for days or weeks. These are the ten signs that most commonly get missed, and what each one might mean.

There is a reason cats are known as stoic. Vulnerability in the wild is dangerous, and domestic cats retain their ancestors' instinct to conceal weakness. This makes them rewarding, self-sufficient companions. It also makes them genuinely difficult to read when something is wrong.

The cats who are brought to us after owners say "she seemed fine yesterday" are, in our clinical experience, never truly fine the day before. The signs were there. They were just the kind of signs that sit easily in the category of "a bit quiet" or "probably nothing" until they are not. This article is designed to shift that threshold, to make the signs recognisable before the condition has become advanced, and to give owners the tools to act earlier.

The 10 Signs Most Commonly Missed

Each of the following signs can indicate illness in cats. None of them, in isolation, means a diagnosis. All of them, sustained for more than 24 to 48 hours or occurring in combination, warrant a veterinary assessment.

1

Changed water intake

A cat drinking noticeably more or less than usual is a significant clinical flag. Increased water intake (polydipsia) is associated with kidney disease, diabetes mellitus, hyperthyroidism, liver disease, and several other systemic conditions. It is one of the earliest observable signs of serious illness in cats, and it is easily overlooked in multi-cat households or when water is not obviously monitored. If you notice your cat at the bowl more often, or if the water level drops faster than usual, note when it started and how significant the change is.

2

Litter box changes

Changes in frequency, volume, consistency, posture, or odour of urine or faeces are among the most informative early indicators of illness in cats. A cat straining in the litter box may have constipation, urinary obstruction, or lower urinary tract disease. A cat urinating outside the litter box may have a urinary infection, renal disease, or diabetes. Loose stools or diarrhoea may indicate dietary issues, parasites, inflammatory bowel disease, or infection. Urine that smells strongly of sweet or acetone-like odour may indicate diabetes. The litter box is a diagnostic window. Use it.

3

Hiding or withdrawal

All cats hide sometimes. It is normal behaviour for a cat who wants quiet, recovery time after a stressful event, or undisturbed rest. What is not normal is a cat who hides persistently, who does not emerge for meals, who avoids interaction with familiar people, or whose choice of hiding location has changed. A cat hiding in a high location (seeking safety above perceived threat) or in a very enclosed space is often a cat experiencing fear or pain. A cat hiding in an unusual place and not responding to encouragement is a cat that needs checking.

4

Weight loss

Weight loss in cats is almost always clinically significant. Unlike in dogs, where weight fluctuation can have benign causes, sustained weight loss in a cat represents a meaningful physical change that should be investigated. The challenge is that weight loss is gradual and easy to miss in a cat who is still eating and active. Running your hands along your cat's spine and ribcage monthly gives a useful baseline: if ribs and vertebrae are more prominent than they were, weight has been lost. Causes include hyperthyroidism, renal disease, diabetes, neoplasia, dental disease, and intestinal malabsorption.

5

Coat changes and reduced grooming

Cats are fastidious groomers. A cat who stops grooming, whose coat becomes dull, matted, greasy, or unkempt, is a cat whose physical capability or motivation to groom has changed. This is associated with dental pain, arthritis (which makes the twisting required for full-body grooming painful), generalised illness, and obesity. Conversely, a cat grooming obsessively at one area may be experiencing localised pain, skin disease, or a neurological issue. Both extremes are meaningful.

6

Bad breath or changed mouth odour

A cat's breath should not be strongly odorous. A sweet or acetone-like smell may indicate diabetic ketoacidosis, which is a medical emergency. An ammonia-like or uraemic smell may indicate advanced kidney disease. Foul, fetid breath is commonly associated with dental disease and oral ulceration. Any sudden or persistent change in your cat's mouth odour warrants investigation, particularly if combined with other signs.

7

Vomiting, especially if repeated

Cats vomit occasionally, and a single episode without other signs is not necessarily alarming. What is significant: vomiting more than once or twice per week consistently; blood in the vomit; vomiting combined with other signs such as lethargy, weight loss, or appetite change; vomiting that contains material suggesting an obstruction; or a sudden change in the frequency of vomiting in a cat who vomits occasionally. Regular vomiting is not simply "what cats do." It is a sign that should be investigated.

8

Eye and nasal discharge

Discharge from the eyes or nose, particularly if persistent, coloured (yellow or green), or associated with sneezing and appetite loss, indicates upper respiratory infection, which is common in cats. Clear discharge may be less urgent than coloured discharge, but any persistent ocular or nasal discharge warrants assessment. In a previously vaccinated, otherwise healthy cat, a mild respiratory event may resolve. In an unvaccinated cat, a kitten, or an immunocompromised cat, upper respiratory infection can progress rapidly.

9

Changes in vocalisation

A cat who becomes more vocal than usual, particularly at night or seemingly without trigger, may be experiencing pain, cognitive decline, hyperthyroidism, or sensory loss. Older cats with hypertension (high blood pressure) sometimes show increased vocalisation. A cat who becomes unusually quiet and stops vocalising at their normal level is also worth noting. Changes in how and when a cat communicates can indicate a range of systemic conditions.

10

Difficulty jumping or changed movement

A cat who stops using the cat tree, avoids the bed they normally sleep on, or seems stiff getting up from rest may be experiencing joint pain. Feline osteoarthritis is significantly underdiagnosed because cats adapt their behaviour rather than complaining. By the time a cat is visibly limping, the condition is usually advanced. Subtle movement changes, such as a shorter jump arc, a preference for lower surfaces, or a hesitant landing, are early signs worth acting on.

Changes in Water Intake and What They Signal

Because increased water intake is such a significant early indicator of serious illness in cats, it deserves expanded attention beyond the summary above.

Normal water intake for a cat varies depending on diet. Cats on a predominantly wet food diet may drink very little, because much of their hydration comes from food. Cats on dry food drink more. The key is not an absolute volume but a change from your individual cat's established normal pattern.

The conditions most commonly associated with increased water intake in cats:

• Chronic kidney disease (CKD): the most common serious condition in older cats. The kidneys lose the ability to concentrate urine, leading to increased urination and compensatory increased drinking. This is often the first detectable sign of CKD.
• Hyperthyroidism: extremely common in cats over ten years old. The thyroid gland overproduces hormone, increasing metabolic rate, which drives increased appetite, weight loss despite eating, increased activity, and increased thirst.
• Diabetes mellitus: less common than in dogs but significant. High blood glucose leads to glucose spilling into the urine, pulling water with it and causing increased urination and compensatory drinking.
• Liver disease: the liver plays a central role in fluid balance. Hepatic disease can drive thirst through multiple mechanisms.
• Pyometra: in unspayed females, uterine infection drives systemic inflammation and increased thirst alongside other signs.

If you notice increased water intake, note when it started, how significant the change appears, and whether any other signs are present. Annual blood work in cats over seven years old picks up kidney disease, thyroid disease, and diabetes early, often before clinical signs are pronounced. This is one of the reasons we recommend annual screening rather than waiting for signs to develop.

Litter Box Changes: The Most Overlooked Early Indicator

If you have one cat and clean the litter box daily, you already have a reasonable monitoring system for your cat's kidney function, bowel health, and urinary tract. Most owners do not think of it this way, but that is exactly what daily litter box awareness provides.

Changes that warrant attention

• More urination than usual, particularly if combined with increased thirst.
• Less urination than usual, or absence of urination in 24 hours: this is an emergency, particularly in male cats, who are at risk of urethral obstruction.
• Blood in the urine (which may appear pink or reddish, or show as reddish staining in the litter).
• Straining in the litter box without producing anything, or producing very small amounts.
• Urinating outside the litter box in a cat who does not normally do so.
• More frequent defecation or loose, liquid stools.
• Absence of defecation for more than two days, particularly in older cats.
• Mucus or blood in faeces.

Emergency: Urinary obstruction in male cats is a life-threatening emergency. A male cat who is visiting the litter box repeatedly without producing urine, who is crying out in the litter box, or who is straining and licking obsessively at his hindquarters needs emergency veterinary care immediately. Do not wait.

Hiding Behaviour in Cats: Normal vs Concerning

Understanding when hiding is normal requires knowing your individual cat's baseline. A cat who hides daily in the same spot as part of their routine is different from a cat who suddenly begins hiding and does not come out for meals, interaction, or play.

Normal hiding

• A brief retreat to a quiet spot after a stressful event (a visitor, a loud noise, a vet visit, a new arrival in the home).
• Seeking a cool, quiet spot in warm weather.
• Rest in a preferred secluded sleeping location the cat returns to regularly.

Concerning hiding

• Persistent hiding across multiple hours or days, particularly if the cat is not coming out for meals.
• Hiding in an unusual location not previously used, particularly if cramped or difficult to access.
• Hiding combined with any other sign listed in this article.
• A cat who hisses, growls, or shows uncharacteristic aggression when disturbed in their hiding spot.
• A cat who is hiding and appears cold, rigid, or minimally responsive when checked.

In our clinical experience, a cat who is hiding and will not come out for food has passed the threshold of "probably nothing." This cat needs to be assessed.

Weight Loss and Coat Change

These two signs frequently occur together because many of the conditions that cause weight loss also affect the cat's energy levels, hormone balance, and capacity to maintain normal grooming behaviour.

How to monitor weight at home

Monthly body condition assessment is the most practical home monitoring tool. Run your hands firmly along your cat's ribcage: in a healthy-weight cat, you should be able to feel the ribs without pressing hard, but they should not be immediately prominent. The same applies to the spine: individual vertebrae should not be sharply palpable. If what you feel has changed from one month to the next, that change is clinically relevant.

If you have a cat who is at risk of weight loss due to age or known conditions, weigh them monthly using the step-on-hold-cat method with household scales. The absolute number matters less than the trend.

Coat changes to watch for

• A coat that was previously smooth and shiny becoming dull, dry, or staring.
• Matting, particularly along the back and hindquarters, which the cat cannot reach easily.
• Increased shedding beyond seasonal norms.
• Flaking or dandruff.
• Greasiness or an altered skin odour.
• Alopecia (hair loss) in patches or generalised thinning.

The Feline Grimace Scale Explained

The Feline Grimace Scale (FGS) is a validated pain assessment tool developed at the University of Montreal, published in 2019, and now widely used in clinical veterinary settings. It was developed in response to a recognised gap: existing pain scales for cats were less reliable than those for dogs, and pain in cats was being systematically underrecognised and undertreated.

The FGS assesses five facial action units, each of which changes predictably in a cat experiencing pain:

Facial action unit

Relaxed / not in pain

In pain

Orbital tightening

Eyes fully open, soft, relaxed

Eyes partially or fully closed; squinting or squeezing

Nose and cheek flattening

Rounded nose and cheeks

Flattened nose; cheeks appear pulled back

Whisker position

Whiskers forward and fanned out naturally

Whiskers pulled back flat against face or bunched

Ear position

Ears forward and open

Ears rotated out and back; flattened

Head position

Head level with or above shoulder line

Head tilted down below shoulders

Each unit is scored from 0 (absent) to 2 (obvious), and a total score of 4 or above out of 10 indicates the cat is likely experiencing pain requiring intervention. The FGS can be applied by a trained observer in real time and is also used with photographs, which means owners who photograph or video their cat at home can sometimes provide useful clinical data before even arriving at the clinic.

At Aura, the Feline Grimace Scale is used as part of pain assessment for all cat patients where pain is a clinical concern. It is particularly useful for cats who are stoic in other ways, because the facial changes are involuntary and cannot be suppressed even by a cat who is masking other signs.

If you want to see what the Feline Grimace Scale looks like in practice, the University of Montreal has published a free FGS manual with reference photographs available online. Familiarising yourself with the relaxed and painful faces gives you a significantly more refined ability to assess your own cat's experience.

Vomiting: When It's Normal and When It's Not

Cats vomit. This is true. But "cats vomit" has become a cultural excuse to ignore a clinical sign that, in many cases, is meaningful.

Vomiting that is generally lower concern

• An isolated single vomiting episode in an otherwise well cat who is eating, drinking, and behaving normally.
• A hairball brought up occasionally (monthly or less) in a long-haired cat.
• Vomiting once after eating unusually quickly.

Vomiting that warrants veterinary assessment

• Vomiting more than once or twice per week consistently, regardless of what is in the vomit.
• Vomiting that contains blood (which may appear red and fresh, or dark and granular like coffee grounds).
• Vomiting combined with weight loss, appetite change, lethargy, or increased thirst.
• Vomiting in a cat who is also not defecating normally.
• Vomiting that began suddenly and has not resolved in 24 to 48 hours.
• A cat who is repeatedly retching or attempting to vomit without producing anything.

Vomiting that is an emergency

• Repeated vomiting over a short period, particularly if the cat is deteriorating rapidly.
• Vomiting of blood with other signs of systemic illness.
• A cat who cannot keep water down.
• A distended, painful abdomen alongside vomiting.

What to Do When You're Not Sure

The uncertainty is the point. Most owners who call us with a concern begin with some version of "I'm not sure if this is something, but..." and that instinct, even when vague, is worth following.

Here is a practical framework for the moments of uncertainty:

Observe for 24 hours if

The cat is eating (even if less than usual), is drinking, has used the litter box, and has no obvious physical signs. One quiet day is not necessarily a sick day. Two quiet days are worth calling about.

Call your vet today if

• You have noticed more than one sign from this article simultaneously.
• A sign that was present yesterday is worse today.
• Your cat has not eaten for 48 hours.
• Something about your cat simply feels wrong, even if you cannot articulate it specifically.

That last point is not trivial. Owners who know their cats well often detect illness before any single sign is definitive. If something feels different, describe what you have noticed as precisely as you can and let a clinician assess it.

Go directly to emergency care if

• Your cat is unable to stand, is collapsed, or is extremely unresponsive.
• Your cat is breathing with effort, open-mouthed, or showing blue gums or tongue.
• A male cat is straining to urinate without producing anything.
• Your cat has had a seizure or is showing neurological signs.
• Your cat has been vomiting repeatedly and is now refusing water.

Cats who are brought in early, when signs are subtle, have significantly better outcomes than cats who are brought in when those signs have progressed. The cost of an unnecessary consultation is an hour of your time and the reassurance that your cat is well. The cost of waiting when you should not have can be considerably higher.

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Written by the Aura Veterinary Clinical Team | Aura Veterinary Center, Dubai