Cat Diarrhoea: Causes and When to See a Vet

When it's an emergency

Contact your vet straight away if your cat:

• Has frequent, watery diarrhoea, especially if it is a kitten or an older cat
• Is also vomiting repeatedly
• Has a lot of blood in the stool, or black, tarry faeces
• Seems weak, very quiet, wobbly or has collapsed
• Has stopped eating, or won't drink
• Has a painful or swollen tummy
• May have eaten something toxic, such as lilies, medicines or household chemicals
• Is straining in the litter tray. Straining can be mistaken for constipation or diarrhoea, but it may be a urinary blockage, which is an emergency

When to book an appointment

Call your vet within a day if:

• Diarrhoea has lasted longer than 24 to 48 hours
• There are small streaks of blood or mucus
• Your cat is eating less than usual
• Diarrhoea keeps coming back over weeks or months
• Your cat is losing weight, drinking more or seems hungrier than normal

What counts as diarrhoea?

Healthy cat faeces are usually well-formed, firm enough to pick up cleanly and mid to dark brown. Diarrhoea means stools that are looser than your cat's normal, more frequent, or both.

What you see	What it may suggest
Soft but formed, one-off	Minor upset, often diet-related
Shapeless, cow-pat consistency	Ongoing upset; watch closely, call if it lasts
Watery, frequent	Risk of dehydration; call your vet
Mucus or jelly-like coating	Large bowel irritation
Fresh red blood	Bleeding in the lower gut; call your vet
Black, tarry stools	Possible bleeding higher up; call urgently
Accidents outside the tray	Urgency, or discomfort

Bringing a photo, or a fresh sample in a clean container if your vet asks, helps a great deal.

Common causes of diarrhoea in cats

Diarrhoea is a symptom, not a diagnosis, and has many possible causes. Some of the more common include:

• Diet changes. Switching food suddenly, rich treats or new snacks.
• Milk and dairy. Many adult cats don't digest lactose well, so cow's milk can cause loose stools.
• Eating things they shouldn't. Hunting, scavenging or eating plants or string.
• Parasites. Roundworms, tapeworms and other gut parasites, particularly in kittens and cats who hunt. See fleas, ticks and worms.
• Infections. Bacterial, viral or protozoal infections, some of which are more common in kittens and in multi-cat homes.
• Stress. Moving house, boarding, or changes in routine.
• Food sensitivities.
• Longer-term conditions, such as inflammatory bowel disease, hyperthyroidism, pancreatic or liver disease, and some cancers, particularly in middle-aged and older cats.
• Toxins and medicines.

Your vet may examine your cat, test a stool sample and sometimes recommend blood tests or imaging to find the cause.

What to do while you watch a mild case

If your cat has had one or two loose stools but is otherwise bright and eating, these steps are sensible:

1. Keep fresh water available. Offer several bowls around the house. If your cat eats wet food, this also adds fluid.
2. Don't stop feeding without advice. Unlike dogs, cats can become seriously unwell if they go without food for even a couple of days, because their body can struggle to process stored fat. Ask your vet before withholding food or changing diet.
3. Remove extras. Stop treats, milk and table scraps while their tummy settles.
4. Keep an eye on the tray. Note how often your cat goes, what the stools look like, and whether they strain or cry.
5. Keep them clean. Long-haired cats may get faeces stuck in the fur around their bottom. Gently clean with warm water and a soft cloth, or carefully trim matted fur.
6. Check for other signs. Vomiting, lethargy, hiding or not eating mean it's time to call your vet.
7. Don't give human anti-diarrhoea medicines. Some are harmful to cats. Only give medicines prescribed by your vet.

If you have more than one cat, try to work out which one is affected. Separate trays or a quick check after each visit can help.

Kittens and older cats

Kittens are small and can lose fluids quickly. They are also more likely to have parasites or infections. Any kitten with diarrhoea, particularly if they seem quiet or aren't eating, should be checked by a vet the same day.

Older cats are more likely to have underlying conditions, and diarrhoea alongside weight loss, increased thirst or a big appetite is worth investigating. Our guide on caring for a senior cat covers other changes to watch for.

Helping prevent tummy upsets

• Change diets gradually, over a week or more, mixing old and new food.
• Avoid cow's milk and fatty human foods.
• Keep up with worming and flea treatment as advised by your vet.
• Keep string, elastic bands and toxic plants out of reach.
• Keep litter trays clean, to make changes easier to spot.

Know your cat's normal

Cats often toilet privately, so changes in stools are easy to miss until they are well established. Taking a quick look when you scoop, and noting anything unusual, gives you a much clearer picture. Petopedia lets you keep a log of food, water, weight and behaviour, so you can see whether loose stools followed a food change, a stressful week or a drop in appetite, and share that timeline with your vet.