Cat Diarrhoea: Causes, Home Care and When to See a Vet

Reviewed by Dr. Ameer Hamza, DVM

Diarrhoea is one of the most common reasons cat owners call their vet. It ranges from a single episode of soft stool that resolves within 24 hours to a persistent, debilitating problem with serious underlying causes. The challenge is knowing which kind you are dealing with — and whether it requires urgent attention or can be managed at home. This guide covers the most common causes, what you can do at home for mild cases, and the signs that require immediate veterinary care.

Acute vs Chronic Diarrhoea

The distinction matters for diagnosis and management. Acute diarrhoea comes on suddenly and lasts less than two weeks. It is most commonly caused by dietary changes, dietary indiscretion (eating something unsuitable), stress, or infection. Most acute cases resolve with supportive care. Chronic diarrhoea persists beyond two to three weeks, or recurs regularly. It more commonly indicates a structural or immune-mediated problem — inflammatory bowel disease, food sensitivity, intestinal parasites, or systemic disease such as hyperthyroidism or liver disease. Chronic diarrhoea almost always requires veterinary investigation with laboratory tests and potentially imaging or intestinal biopsies to diagnose.

Common Causes

Dietary causes are the most common trigger for acute diarrhoea. Switching food brands too rapidly, feeding rich or unusual foods, ingesting dairy products (most cats are lactose intolerant), scavenging inappropriate food, or eating plants can all cause acute loose stools. Always transition between cat foods over 7–10 days by gradually increasing the proportion of new food to avoid digestive upset. Intestinal parasites including Giardia, roundworms, and Tritrichomonas are common causes, particularly in kittens and cats with outdoor access. A stool sample examination at the vet can diagnose these. Viral and bacterial infections including feline parvovirus (panleukopenia) and Campylobacter can cause acute, sometimes severe diarrhoea. Stress — moving house, new pets, changes in routine — triggers diarrhoea in many cats. Inflammatory bowel disease (IBD) is a chronic immune-mediated condition causing persistent small intestinal or large intestinal inflammation; it is common in cats over seven and causes chronic weight loss, vomiting, and diarrhoea. Food intolerance or allergy — a reaction to a specific protein or ingredient — causes chronic or recurring diarrhoea that resolves completely on an elimination diet.

Emergency Signs That Require Immediate Vet Attention

Go to a vet immediately if your cat shows any of the following: blood in the stool (fresh red blood or dark, tarry black stools); weakness, lethargy, or collapse alongside diarrhoea; vomiting combined with diarrhoea preventing any fluid retention (dehydration risk is severe); marked abdominal pain or bloating; or if the affected cat is a kitten, elderly, or already unwell for any other reason. Kittens with severe diarrhoea can become critically dehydrated within hours. Black tarry stools indicate digested blood from upper gastrointestinal bleeding and are a serious sign at any age.

Home Management for Mild Acute Cases

For an otherwise healthy adult cat with a single episode or mild acute diarrhoea lasting less than 24 hours with no blood, vomiting, or systemic signs, supportive home management is appropriate: feed small amounts of a bland, easily digestible diet — boiled plain chicken, a prescription GI diet, or a simple commercial food your cat tolerates well. Feed smaller portions more frequently rather than one or two large meals. Ensure clean water is always available and monitor for signs of dehydration (sunken eyes, dry gums, skin that stays tented when gently pinched). Veterinary-specific probiotics (Fortiflora) can be added to food to support gut flora recovery. Monitor for improvement within 24–48 hours.

What Not to Do

Do not withhold all food entirely — unlike dogs, cats are vulnerable to hepatic lipidosis when not eating and fasting is not recommended for more than a few hours. Do not give human anti-diarrhoea medications such as Imodium (loperamide) without veterinary guidance — loperamide can be toxic to cats at certain doses. Do not give dairy products in the hope that they settle the stomach — most cats cannot digest lactose and dairy will worsen diarrhoea. Do not ignore blood in the stool or signs of systemic illness in the hope they resolve spontaneously.

Veterinary Diagnosis and Treatment

For persistent, severe, or unexplained diarrhoea, vets will typically perform a physical examination, run blood and biochemistry panels to assess organ function and look for systemic disease, and request a faecal sample to test for parasites. For chronic cases, additional investigations including intestinal ultrasound, endoscopy, and intestinal biopsies may be needed to diagnose IBD, lymphoma, or other structural disease. Treatment depends on the underlying cause: antiparasitic drugs for parasites; dietary trials (novel protein or hydrolysed protein diets) for food sensitivity; immunosuppressants for IBD; and disease-specific management for hyperthyroidism, liver disease, or other systemic conditions.

Frequently Asked Questions

What are the most common causes of diarrhoea in cats?

Dietary changes, dietary indiscretion, stress, intestinal parasites, and infection for acute cases. IBD, food sensitivity, hyperthyroidism, and intestinal lymphoma for chronic cases.

When should I take my cat to the vet?

Immediately if there is blood in the stool, the cat is weak or lethargic, vomiting prevents fluid retention, or the affected cat is a kitten or elderly. After 48 hours for mild cases that are not improving.

Can I feed my cat normally when they have diarrhoea?

Feed a bland, easily digestible diet in smaller portions. Do not withhold all food — cats are vulnerable to fatty liver disease when fasted.

Do probiotics help?

Veterinary-specific probiotics can help restore gut flora, particularly for stress-related or post-antibiotic diarrhoea. Use products formulated for cats, not human probiotics.

Can stress cause diarrhoea in cats?

Yes — stress is a common trigger. Moving house, new pets, or changes in routine can all precipitate acute diarrhoea. Address the underlying stress for recurrent stress-related cases.

For a full overview of cat health, see the complete cat care guide.

---

Disclaimer: This article is for educational purposes only. Diarrhoea with blood, systemic illness, or that persists more than 48 hours requires veterinary assessment — do not delay seeking professional care.