Cats are experts at hiding illness. By the time a cat looks obviously unwell, a problem has often been building for a while. The early clues are usually small changes in everyday habits: eating a little less, hiding more, skipping a jump onto the sofa, or spending longer in the litter box. You know your cat’s normal better than anyone, and noticing when something is off is the most useful thing you can do.
Quick answer: Watch for changes in appetite, thirst, litter box habits, energy, grooming, breathing and behavior. Hiding, weight loss, vomiting, diarrhea and a scruffy coat are common early signs. A cat that hasn’t eaten for 24 hours needs a vet. Straining to pee with little or nothing coming out, breathing with the mouth open, seizures, collapse or repeated vomiting are emergencies.
Why cats hide illness
Cats are both hunters and prey animals, and showing weakness can make an animal a target. As a result, many cats carry on as normal for as long as they can, then quietly withdraw when they feel unwell. That is why small changes matter. A cat that “just seems a bit off” for more than a day or two is worth a closer look, even if you can’t put your finger on what’s wrong.
Signs of illness at a glance
| What you notice | What to do |
|---|---|
| Straining to pee with little or no urine, especially in a male cat | Emergency: go to a vet now |
| Open-mouth breathing, panting, or struggling to breathe | Emergency: go to a vet now |
| Seizure, collapse, unresponsiveness, or vomiting that won’t stop | Emergency: go to a vet now |
| Not eating for 24 hours | See a vet today |
| Vomiting or diarrhea lasting more than a day, or with lethargy | See a vet within a day |
| Drinking or peeing more, weight loss, eye or nose discharge | Book a vet appointment soon |
| Hiding more, less grooming, mild personality change | Watch closely; book a check if it lasts more than a day or two |
Changes in eating, drinking and weight
Eating less or not at all. This is one of the most common signs that a cat isn’t well. Cats shouldn’t go without food: VCA advises seeking veterinary care if a cat hasn’t eaten for 24 hours.
Eating much more than usual. A sudden big appetite, especially with weight loss, can point to problems such as an overactive thyroid or diabetes and needs a vet check.
Drinking more. If you are refilling the water bowl more often, or your cat is drinking from taps and glasses, mention it to your vet. Increased thirst can be linked to kidney disease, diabetes and other conditions. A cat that drinks less than usual can also be a concern; see why your cat may not be drinking much water.
Weight loss or gain. Gradual weight loss is easy to miss in a fluffy cat. If you can feel the spine or ribs more easily when stroking, or your cat feels lighter when you lift it, book a check. Unexplained weight gain is worth discussing too.
Litter box changes
The litter box tells you a lot about your cat’s health. Look out for:
- Peeing more or less than usual, or larger or smaller clumps
- Straining, crying or spending a long time in the box
- Peeing or pooping outside the box
- Diarrhea, very hard, dry stools, or blood in the stool or urine
Urgent: a cat, especially a male cat, that keeps going to the litter box and straining but produces little or no urine may have a blocked bladder. This can become life-threatening quickly. Go to a vet immediately.
For more detail, see our guides to cats peeing outside the litter box, diarrhea in cats and cat constipation.
Vomiting and hairballs
Many owners think frequent vomiting is normal for cats. It isn’t, and regular vomiting, even of hairballs, is worth discussing with your vet. Vomiting that is repeated, contains blood, comes with lethargy or a poor appetite, or won’t stop needs prompt care. Our guide to cat vomiting explains what to watch.
Behavior and energy changes
- Hiding more than usual, or no longer greeting you
- Sleeping more, playing less, or seeming dull and flat
- Personality changes: a friendly cat becoming irritable, or an independent cat becoming clingy
- New or different meowing, especially at night, or crying out
- No longer jumping onto favorite spots, or moving stiffly
- Restlessness or unusual hyperactivity
Many of these can also be signs of pain. Our guide to signs your cat is in pain goes into more detail.
Grooming, coat and skin
A healthy cat keeps itself tidy. A cat that stops grooming may develop a greasy, scruffy or matted coat, which can be a sign of illness, pain or dental problems. Overgrooming, bald patches, scabs or constant scratching can point to fleas, allergies, skin infections or stress. See our guide to fleas and ticks on cats if your cat is itchy. Any new lump or swelling should be checked by your vet.
Breathing, eyes, nose and mouth
Breathing. Cats don’t normally pant. PetMD notes that panting or open-mouth breathing in a cat can signal stress, overheating or serious heart or lung disease. Fast breathing while resting, wheezing or coughing also need a vet. Labored breathing is an emergency.
Eyes and nose. Discharge, redness, squinting, a third eyelid showing, or pupils of different sizes all deserve attention. Sneezing with eye and nose discharge often points to an upper respiratory infection.
Mouth. Bad breath, drooling, dropping food, chewing on one side or pawing at the mouth can be signs of dental disease. Gums that look pale, white, blue or yellow are a reason to see a vet urgently.
Kittens and senior cats
Kittens can become seriously ill quickly, especially with vomiting, diarrhea or not eating, because they dehydrate fast. Don’t wait to see if a sick kitten improves. Keep vaccinations on schedule; see our cat vaccination schedule.
Senior cats often develop problems slowly, such as kidney disease, an overactive thyroid, arthritis and dental disease. Changes in thirst, weight and mobility are easy to put down to age, but many are treatable. Regular senior checkups help catch them early. See common health problems in senior cats.
Simple checks you can do at home
These won’t diagnose anything, but they help you tell your vet what’s changed:
- Appetite and water: roughly how much is your cat eating and drinking compared with normal?
- Litter box: how many clumps of urine, what the stool looks like, and any blood or straining
- Weight: weigh your cat on home scales (weigh yourself holding the cat, then subtract your own weight) and note it down
- Gums: they should look pink and feel moist, not pale, white, blue, yellow or sticky
- Hydration: sunken eyes, sticky gums, or skin that doesn’t spring back quickly when gently lifted can be signs of dehydration
A warm or dry nose on its own tells you very little about whether a cat is sick. Look at the whole cat instead.
When it’s an emergency
Urgent: go to a vet straight away if your cat is straining to pee with little or nothing coming out, breathing with its mouth open or struggling to breathe, has a seizure, collapses, can’t stand, is unresponsive, has vomiting that won’t stop, has pale or blue gums, or may have eaten something poisonous such as lilies, medicines or antifreeze.
If you think your cat has eaten something toxic, don’t try to make it vomit. Call your vet or an animal poison line immediately, and take the packaging or plant with you if you can. Our guide to plants and foods poisonous to cats lists common dangers, and cat first aid basics covers what to do on the way.
Helping your vet
Before your appointment, note when you first noticed the change, what your cat has eaten and drunk, any vomiting or diarrhea (photos can help), litter box changes, any medicines or flea treatments given, and whether anything changed at home recently. Short videos of odd breathing, limping or behavior are useful, since cats often act differently at the clinic. A calm carrier routine makes the trip easier too.
Frequently asked questions
How do I know if my cat is sick or just tired?
A tired cat still eats, uses the litter box normally, grooms, and perks up for food or play. A sick cat often shows other changes too, such as hiding, eating less, a scruffy coat or litter box changes. If your cat seems dull for more than a day, or has any other signs, contact your vet.
How long can a cat go without eating?
Not long. VCA advises getting veterinary care if a cat hasn’t eaten for 24 hours. Cats that stop eating can quickly develop serious problems, so don’t wait several days to see if the appetite returns.
Is a dry or warm nose a sign my cat is sick?
Not on its own. A cat’s nose can be warm or dry for many harmless reasons. Changes in appetite, energy, breathing, litter box habits and behavior are far more useful signs.
Is it normal for cats to vomit often?
No. Occasional hairballs can happen, but regular vomiting isn’t normal and is worth raising with your vet. Vomiting that is frequent, contains blood, or comes with lethargy or poor appetite needs prompt attention.
