Moderate severity

Diarrhoea

Loose, watery or more frequent stools — a very common sign in cats that ranges from a passing upset to a warning of infection, parasites or a more serious underlying illness.

⚠️ Common symptoms

Loose, soft or watery stoolsMore frequent trips to the litter boxStraining or urgency, sometimes with accidents outside the boxBlood or mucus in the stoolA foul or unusual smellReduced appetite, low energy or a bloated, gurgly bellySigns of dehydration if it goes on — dry gums, sunken eyes, lethargy

Diarrhoea is one of the signs cat owners meet most often, and while a single soft stool is rarely cause for alarm, it is worth understanding because it can mean anything from a trivial tummy upset to the first hint of a serious disease. At its simplest, diarrhoea happens when food moves through the intestines too quickly, or when the gut fails to absorb water properly, so stools arrive loose, watery and more frequent than normal. The trick is reading the wider picture: how long it has lasted, how the cat is otherwise, and what the stool looks like.

Doctors and vets find it useful to think about where in the bowel the trouble lies. Diarrhoea from the small intestine tends to produce large volumes of watery stool, weight loss and sometimes vomiting, while diarrhoea from the large intestine (the colon) typically brings smaller amounts passed with straining and urgency, often streaked with fresh red blood and mucus. Neither picture names the cause on its own, but it helps steer the search.

The list of causes is long. In kittens, parasites and infections dominate — worms, giardia, coccidia and viruses like panleukopenia. In adults, a sudden diet change, scavenging, or a food intolerance is a frequent and fixable culprit. When diarrhoea drags on for weeks, the focus shifts to conditions such as inflammatory bowel disease, an overactive thyroid, pancreatitis, and liver or kidney disease, while in older cats intestinal lymphoma has to be considered. Because the possibilities are so broad, a vet works methodically through stool tests, blood work and sometimes imaging rather than guessing.

For a bright, well cat with mild diarrhoea, sensible home care is reasonable for a day or two: keep water available, offer a bland digestible diet, and let the gut settle. But three things should always send you to the vet — diarrhoea that persists, diarrhoea in a kitten or frail older cat, and any diarrhoea alongside blood, vomiting, pain, or a cat that has gone flat and off its food. The greatest danger from ongoing diarrhoea is dehydration, which small cats reach alarmingly quickly, so when in doubt it is always safer to have it checked. Crucially, resist reaching for human anti-diarrhoeal remedies: several, including products containing salicylates, are poisonous to cats.

🔍 Causes

Diarrhoea is a symptom with many possible causes. Common triggers include a sudden change of diet, dietary indiscretion (eating something they should not), food intolerances and allergies, and intestinal parasites such as worms, giardia and coccidia. Infections — viral, bacterial or protozoal — are frequent culprits, particularly in kittens. Longer-lasting diarrhoea can signal inflammatory bowel disease, pancreatitis, an overactive thyroid, liver or kidney disease, or, in older cats, intestinal cancer. Stress and certain medications can also loosen the bowels.

🛡 Prevention

Make any diet change gradually over a week or so to let the gut adjust, and keep cats away from spoiled food, rubbish and houseplants. Keep up routine deworming and parasite control, provide clean fresh water, and maintain vaccinations to guard against infectious causes. In multi-cat homes, plenty of clean litter boxes and good hygiene limit the spread of infectious diarrhoea. Managing stress and sticking to a consistent, good-quality diet keep most cats' digestion settled.

💊 Treatment

Mild, short-lived diarrhoea in an otherwise well adult cat is often managed with simple supportive care: ensuring constant access to water, feeding a bland, easily digested diet for a few days, and sometimes a vet-recommended probiotic or fibre supplement to help firm the stool. Persistent or severe cases need a vet to find the cause — this may involve stool tests for parasites and bacteria, deworming, blood work, and treatment aimed at the underlying problem, whether that is a parasite, an infection, a food intolerance, or a condition such as inflammatory bowel disease or hyperthyroidism. Never give human anti-diarrhoeal medicines, as several are toxic to cats.

When to see a vet: See a vet promptly if diarrhoea lasts more than a day or two, contains a lot of blood, is black and tarry, or comes with repeated vomiting, a painful belly, fever or obvious lethargy. Kittens, elderly cats and those with existing illnesses dehydrate dangerously fast, so their diarrhoea should never be left to run its course — seek care early. Any cat that stops eating and drinking, or seems weak and unwell alongside the diarrhoea, needs urgent attention.

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⚕️ Medical disclaimer

This information is educational only and is not a substitute for veterinary advice.
Symptoms overlap between conditions — only a vet can diagnose accurately.
Never withhold treatment or self-medicate based on information found online.
When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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