Loose stools are messy, but the real worry is what they can take with them: water, salts, and a cat’s comfort. A single soft poo after a diet change may pass quietly. Diarrhoea that keeps going, or arrives with vomiting, lethargy, or blood, can tip into dehydration fast—especially in kittens and older cats.1, 2
Below is a clear, practical way to judge what you’re seeing, what you can safely do at home, and the points where a vet visit matters. The aim is steadiness: support the gut, protect hydration, and avoid the common missteps that make diarrhoea drag on.
What counts as diarrhoea in cats
Diarrhoea means stools that are softer than normal, more frequent than normal, or watery. It can be a short-lived upset, or a sign of disease inside (or outside) the gut. When food moves too quickly through the intestines, the body absorbs less water and electrolytes—so the stool stays loose and the cat can gradually dry out.1
Common causes
Diet change, rich food, or scavenging
Sudden food switches, new treats, table scraps, and raiding the bin are classic triggers. Even a good-quality new food can cause a brief wobble if the transition is rushed.1, 2
Parasites and infections
Intestinal parasites (including Giardia) can cause ongoing or intermittent diarrhoea, sometimes with greasy-looking, foul-smelling stools and mucus. Infection spreads by the faecal–oral route—contaminated paws, fur, litter trays, and shared environments all matter—so hygiene is part of treatment, not an afterthought.3
Stress and sudden routine shifts
Travel, boarding, household changes, and conflict with other pets can coincide with short bouts of diarrhoea. Stress doesn’t “cause” every case, but it can tip a sensitive gut into trouble, or worsen an existing problem.1
Underlying illness (when it keeps coming back)
Repeated or persistent diarrhoea can be linked with inflammatory, infectious, or even cancerous disorders of the gut. It can also reflect problems elsewhere in the body (for example, thyroid disease or kidney and liver disorders). That’s why chronic diarrhoea deserves proper work-up rather than endless food changes.1
Quick triage: when to call a vet
Get veterinary advice urgently if you notice any of the following:
- Diarrhoea lasting more than 24–48 hours.1, 4
- Blood in the stool, black/tarry stool, or lots of mucus.4
- Vomiting, marked lethargy, obvious abdominal pain, or refusal to eat.1, 4
- Signs of dehydration (dry or tacky gums, sunken eyes, weakness).5
- A kitten, very old cat, pregnant cat, or a cat with a known chronic condition—these cats can deteriorate faster.1, 6
- Possible toxin exposure, string/foreign-body risk, or you simply can’t keep fluids down.6
What you can do at home (for mild cases only)
If your cat is bright, comfortable, still drinking, and the diarrhoea is mild and recent, home care is reasonable for a short window. The goal is to protect hydration and give the bowel a calmer workload—without doing anything that could make things worse.
1) Protect hydration first
Offer fresh water at all times. Diarrhoea can quietly drain fluid reserves, and dehydration is one of the main reasons “simple diarrhoea” becomes an emergency.5
If your cat won’t drink, is vomiting, or seems flat and dry-mouthed, skip home tinkering and call your vet. Cats that are hypovolaemic (poor circulation from fluid loss) need veterinary fluid therapy, typically via IV or intraosseous routes.7
2) Keep food simple and small
For adult cats who are otherwise well, a brief “gut rest” can help—then reintroduce food in small, frequent meals. One practical approach used in veterinary advice is withholding food for around six hours (not for kittens), then offering a bland, easily digested diet for a couple of days before gradually returning to the usual food.6
Avoid fatty foods, milk, rich treats, and sudden diet swaps. If your cat needs a food change, do it gradually once things settle.
3) Watch the litter tray like a field notebook
Track what changes, and how quickly:
- How often your cat passes stool
- Consistency (soft vs watery), colour, smell
- Mucus, blood, or straining
- Appetite, drinking, vomiting, energy levels
This history helps a vet narrow the likely causes and choose the right tests sooner.1
4) Don’t give human medicines
Some over-the-counter products that are common in people can be dangerous for cats, and even pet-intended anti-diarrhoeals aren’t appropriate in every case. If you’re tempted to medicate, ring your clinic first. Cornell’s feline health guidance also notes that some over-the-counter medications can harm cats.1
What your vet may do (and why)
When diarrhoea persists, returns, or arrives with systemic signs, the job changes from “settle the gut” to “find the cause”. A veterinarian typically starts with a careful history and exam, then chooses tests based on age, severity, and whether the diarrhoea looks like it comes from the small intestine, large intestine, or both.1
Common diagnostic steps
- Faecal testing for parasites and protozoa (including Giardia) and sometimes antigen tests.3
- Blood tests to check hydration status, electrolytes, inflammation, and clues pointing beyond the gut.1
- Imaging (X-ray or ultrasound) if obstruction, mass, or organ disease is suspected.
Treatment options you might see
- Supportive care: fluids (route depends on severity), nausea control if needed, and a highly digestible diet.7
- Parasite treatment: targeted medication when parasites/protozoa are found or strongly suspected.3
- Probiotics and gut-protectants: sometimes used to support recovery; antibiotics are not automatically required and can be unhelpful in the wrong setting.8
Long-term prevention (for cats with repeat episodes)
Feed for consistency, not novelty
Cats with sensitive guts often do best on a steady, high-quality diet with slow transitions when change is necessary. Sudden switches are a common trigger for short-term diarrhoea.2
Parasite control and household hygiene
Pick up faeces promptly, keep litter trays clean, and follow your vet’s parasite-control plan. With Giardia, environmental contamination and reinfection are common hurdles, so hygiene measures are an essential part of control.3
Keep stress low where you can
Predictable feeding, stable routines, and safe resting spots won’t prevent every bout of diarrhoea, but they reduce one common pressure on the gut—especially around travel, visitors, or moving house.1
Natural and alternative remedies: a cautious note
Herbal or “natural” products are often marketed for stomach upsets, but cats metabolise many compounds differently from people and dogs. Evidence and dosing can be thin, and some ingredients are unsafe. If you want to use anything beyond diet and hydration support, run it past your vet first—especially if your cat is on other medications or has ongoing symptoms.
When a specialist is worth it
A referral to an internal medicine specialist (or a vet with a strong gastroenterology focus) is often helpful when diarrhoea is chronic, associated with weight loss, keeps relapsing, or doesn’t respond to sensible first-line management. In these cases, more advanced testing (including gut imaging and sometimes biopsies) can be the difference between guessing and treating with precision.1
References
- Cornell University College of Veterinary Medicine (Cornell Feline Health Center): Diarrhea
- Pet Circle: Causes of Diarrhoea in Cats
- Merck Veterinary Manual (Professional): Giardiasis in Animals
- PDSA: Diarrhoea in cats
- Vets Love Pets (Australia): Signs of Dehydration in Dogs and Cats
- Vet Voice (Australia): What to do if your pet vomits or has diarrhoea
- American Animal Hospital Association (AAHA): 2024 Fluid Therapy Guidelines — Section 3
- PDSA: Diarrhoea in cats — Will my cat need antibiotics?
Veterinary Advisor, Veterinarian London Area, United Kingdom