Cat Diarrhoea: Causes, Treatment and When to Call a Vet

Common causes of diarrhoea in cats

PDSA lists sudden diet change, eating something unsuitable, worms and other gut parasites among common causes. Pancreatitis, infection, inflammatory bowel disease, toxins, a blockage and disease elsewhere in the body are also possible. The same appearance can therefore come from a minor dietary upset or a condition needing treatment.

Stress can alter gut function too, but it should not be used as a diagnosis without considering medical causes. A house move, boarding stay or conflict between cats may be relevant history for your vet, especially if tests do not show another explanation.

• Diet: abrupt food change, excessive treats, spoiled food or human food; milk can cause diarrhoea because many adult cats do not tolerate lactose.
• Parasites: worms, Giardia, Cryptosporidium and Tritrichomonas are among the possibilities.
• Infection or inflammation: bacterial or viral illness, pancreatitis and chronic inflammatory gut disease.
• Medication or toxins: some medicines can upset the gut; suspected poisoning is an emergency.
• Other disease: liver, kidney or endocrine disease and cancer may cause persistent diarrhoea, often with additional signs.

What the stool can and cannot tell you

Normal cat faeces should be brown, formed, moist and easy to scoop. Large-intestinal diarrhoea often appears as frequent small amounts with mucus or fresh red blood, while small-intestinal disease can produce larger volumes of watery stool. These clues help a vet plan tests but do not prove a diagnosis at home.

Black, tarry stool can indicate digested blood from higher in the digestive tract and needs prompt veterinary advice. Fresh red streaks may come from irritation or straining, but infection, inflammation and other disease are possible. Photograph an unusual stool before cleaning it and, if your vet requests one, collect a fresh sample in a clean sealed container.

Safe care for a mild episode

PDSA advises that cats do not need to be starved. If an otherwise well adult cat has had mild diarrhoea for less than a day, offer small frequent meals. Use the cat's usual food if a sudden change may be the trigger, or follow your vet's advice about a short bland or gastrointestinal diet.

Keep several bowls of fresh water available and monitor drinking, urination, appetite and activity. Let the cat rest and keep the litter tray clean so you can judge frequency and appearance. Once stools are firm, transition back to the normal balanced diet gradually over several days.

What not to give a cat with diarrhoea

Do not give human anti-diarrhoeal medicine, leftover antibiotics, painkillers or a random worming product. Some human medicines are toxic to cats, antibiotics can disrupt normal gut bacteria, and parasite treatment needs to match the parasite and the cat's weight and health.

Probiotics help some cats but are not a universal treatment. Ask your vet to recommend a feline product and dose, particularly if the cat takes other medication or has a chronic condition. Avoid rich, fatty foods and milk.

How a vet investigates persistent diarrhoea

Your vet will ask about diet changes, access outdoors, scavenging, medications, parasite prevention, duration and whether there is weight loss or vomiting. Examination includes hydration, temperature, abdominal comfort and body condition.

Depending on the history, tests may include faecal analysis, blood and urine tests, a structured diet trial, x-rays, ultrasound or endoscopy. Treatment can involve diet, fluids, targeted parasite treatment, probiotics or anti-inflammatory medication; surgery may be needed for a blockage. The treatment follows the cause rather than the symptom alone.

Preventing repeat digestive upsets

Change food slowly over about a week unless your vet gives different instructions. Store food as directed, keep bins and string-like objects inaccessible, maintain vet-advised parasite control and avoid feeding milk or frequent table scraps.

For cats that toilet outdoors, provide an indoor tray temporarily if you suspect diarrhoea. This makes frequency and stool appearance visible and helps your vet decide whether the problem is resolving.