Cat Diarrhoea: Causes, Home Treatment & When to See a Vet
Diarrhoea in cats is one of those symptoms that ranges from completely benign to genuinely concerning, and knowing the difference can be difficult for pet parents. A single bout of soft stool after eating something unusual is rarely cause for alarm. But diarrhoea that lasts more than 24 hours, contains blood, or is accompanied by other symptoms like vomiting or lethargy warrants veterinary attention.
The vast majority of diarrhoea cases are mild and self-limiting, but a small proportion are caused by serious underlying conditions that need investigation and treatment. This guide will help you work out which category your cat likely falls into and what to do about it. Key claims are supported by peer-reviewed veterinary and institutional sources listed at the end.
What Is Normal Cat Faeces?
Healthy cat faeces should be firm but not hard, brown in colour, and formed into discrete logs. It should hold its shape when you scoop the litter tray, and while it won't smell pleasant, it shouldn't be overwhelmingly offensive.
Diarrhoea is loose, watery, or unformed stool. It can range from slightly soft to completely liquid, and the frequency of defecation usually increases. The colour, consistency, and presence of blood or mucus all provide important clues about what's causing it.
Common Causes of Diarrhoea in Cats
1. Dietary Indiscretion
The most common cause of acute diarrhoea in cats is eating something they shouldn't have. This might be human food, spoiled food from the bin, a dead animal they caught outside, or simply eating too much too quickly. Dietary indiscretion usually causes a single episode or a day of loose stools that resolves on its own.
2. Sudden Diet Change
Switching foods too quickly is a frequent cause of diarrhoea. Cats have sensitive digestive systems, and even a change from one high-quality food to another can trigger upset if done abruptly. Transitioning foods gradually over 7 to 14 days is generally recommended.
3. Food Intolerance or Allergy
Some cats develop sensitivities to specific proteins or ingredients in their food. Food intolerance typically causes chronic, intermittent diarrhoea rather than a sudden acute bout. Common culprits include beef, dairy, fish, and certain grains. An elimination diet under veterinary guidance is the usual way to identify the trigger.
4. Intestinal Parasites
Worms (roundworms, tapeworms, hookworms) and protozoal parasites (Giardia, Coccidia, Tritrichomonas) are common causes of diarrhoea, particularly in kittens and outdoor cats. You may see worms in the faeces, or the stool may simply be persistently loose. Regular parasite treatment is important for all cats.
5. Inflammatory Bowel Disease (IBD)
IBD is a chronic condition where the walls of the intestine become infiltrated with inflammatory cells. It typically causes persistent or intermittent diarrhoea, often with mucus, alongside weight loss, vomiting, and variable appetite. Diagnosis usually requires intestinal biopsies, and management involves dietary modification and vet-prescribed medication.
6. Infections
Bacterial infections (Salmonella, Campylobacter, Clostridium), viral infections (feline parvovirus/panleukopenia, coronavirus), and fungal infections can all cause diarrhoea. Kittens are particularly vulnerable. Infectious diarrhoea is often accompanied by fever, lethargy, vomiting, and rapid deterioration.
7. Pancreatitis
Inflammation of the pancreas commonly causes diarrhoea alongside vomiting, abdominal pain, and lethargy. Pancreatitis can be acute or chronic and ranges from mild to life-threatening. Diagnosis typically requires blood tests and ultrasound.
8. Hyperthyroidism
An overactive thyroid gland is very common in older cats and can cause increased appetite, weight loss, hyperactivity, and diarrhoea. It is typically diagnosed with a blood test and manageable once treated. For more detail, see our guide on how to treat hyperthyroidism in cats.
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9. Kidney Disease
Chronic kidney disease can cause diarrhoea due to the build-up of toxins in the bloodstream and changes in gut bacteria. Other signs include increased thirst and urination, weight loss, and poor appetite.
10. Stress and Anxiety
Stress is an underestimated cause of diarrhoea in cats. Moving house, a new pet, changes in routine, or even a dirty litter tray can trigger stress-related diarrhoea. It usually resolves once the stressor is removed.
When Is Cat Diarrhoea an Emergency?
Seek immediate veterinary care if your cat:
- Has bloody diarrhoea (bright red or dark, tarry stools)
- Is vomiting repeatedly alongside diarrhoea
- Is lethargic, unresponsive, or collapsed
- Has not eaten or drunk for more than 24 hours
- Is showing signs of dehydration such as sunken eyes, dry gums, or skin tenting when pinched
- Has a high fever (over 39.5°C / 103°F)
- Is a kitten, as young cats can deteriorate rapidly
- Has profuse watery diarrhoea that won't stop
Home Care for Mild Cat Diarrhoea
If your cat has had one or two episodes of soft stool but is otherwise well — eating, drinking, alert, and playful — you can initially manage at home:
- Withhold food for 12 to 24 hours (water should always be available) to give the gut time to rest
- Reintroduce food gradually with small, frequent meals of bland food (plain boiled chicken, white fish, or a prescription gastrointestinal diet)
- Ensure fresh water is always available as cats with diarrhoea dehydrate quickly
- Keep the litter tray clean to monitor stool consistency and frequency
- Monitor closely: if diarrhoea persists beyond 24 hours, or your cat seems unwell, call your vet
Do not give human anti-diarrhoeal medications to cats. Pepto-Bismol (bismuth subsalicylate) is unsafe for cats because cats cannot metabolise salicylates and can develop salicylate toxicity.[1][2] Imodium (loperamide) is off-label and controversial in cats because it can cause opioid-like neurological effects and risks such as ileus.[3] Neither should be given without veterinary direction.
What Does the Colour and Consistency Mean?
- Yellow or orange diarrhoea: May indicate food moving too quickly through the intestines, or liver or gallbladder issues[4]
- Green diarrhoea: May indicate bacterial infection, bile passing through too quickly, or ingestion of grass
- Black, tarry stools: Suggests digested blood from the upper GI tract (stomach, small intestine); needs immediate vet attention[4][5]
- Bright red blood: Suggests bleeding in the lower intestines or rectum; needs same-day vet attention
- Mucus in stool: Suggests inflammation of the large intestine (colitis)
- Watery, explosive diarrhoea: Often an infectious or toxic cause; risk of rapid dehydration
Frequently Asked Questions
How long should cat diarrhoea last?
A single episode or one day of loose stools is not unusual and often resolves on its own. If diarrhoea lasts more than 24 hours, or if your cat seems unwell, contact your vet. Chronic diarrhoea (lasting more than a week) always warrants investigation.
Can I give my cat anything for diarrhoea?
Do not give human anti-diarrhoeal medications. Your vet will decide the right treatment based on examination and the underlying cause. Never medicate your cat without veterinary advice.
Should I withhold food if my cat has diarrhoea?
For mild, acute diarrhoea, withholding food for 12 to 24 hours (with water always available) can help the gut rest. Reintroduce bland food gradually. If diarrhoea persists or your cat seems unwell, see your vet.
Why does my cat have diarrhoea but is acting normal?
Mild dietary upset, stress, or food intolerance can cause diarrhoea without affecting overall demeanour. If your cat is eating, drinking, and acting normally, you can monitor at home for 24 hours. If diarrhoea continues beyond this, see your vet.
Can stress cause diarrhoea in cats?
Yes. Cats are sensitive to environmental changes, and stress from moving house, new pets, or changes in routine can trigger diarrhoea. It usually resolves once the stressor is removed.
Is cat diarrhoea contagious to humans?
Some causes of cat diarrhoea (Salmonella, Campylobacter, Giardia) are zoonotic and can spread to humans. Always wash your hands thoroughly after handling the litter tray, especially if your cat has diarrhoea.
Important: This article is general educational information about diarrhoea in cats and does not constitute veterinary advice for any individual cat. If your cat has diarrhoea that persists, is showing new or worsening symptoms, or you have specific concerns about their health, please consult a registered veterinary surgeon who can examine your cat and provide personalised guidance.
References
- Merck Veterinary Manual. Drugs Used to Treat Diarrhea in Monogastric Animals. Available at: https://www.merckvetmanual.com/pharmacology/systemic-pharmacotherapeutics-of-the-digestive-system/drugs-used-to-treat-diarrhea-in-monogastric-animals
- Papich MG. Saunders Handbook of Veterinary Drugs: Small and Large Animal. 5th ed. Elsevier; 2021. Bismuth subsalicylate — contraindicated in cats due to salicylate toxicity.
- Plumb DC. Plumb's Veterinary Drug Handbook. 10th ed. Wiley-Blackwell; 2023. Loperamide — use in cats is off-label and considered controversial due to opioid-like CNS effects.
- International Cat Care. Diarrhoea in cats. Available at: https://icatcare.org/articles/diarrhoea-in-cats
- Cats Protection. Digestive disorders: vomiting and diarrhoea in cats. Available at: https://www.cats.org.uk/media/1047/vg18_digestive_disorders-_vomiting_and_diarrhoea.pdf
- PDSA. Vomiting and diarrhoea in cats. Available at: https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub
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