Cat Diarrhea: Common Causes, What You Can Do at Home, and When to Call the Vet

Sooner or later, almost every cat produces a litter box surprise: stool that is soft, watery or simply wrong. Most episodes are mild and pass within a day or two. Some are the first sign of something that needs treatment. This guide explains how vets think about feline diarrhea so you can decide what to do and when to pick up the phone.

What Counts as Diarrhea?

Diarrhea is stool with more water than normal, usually passed more often or in larger amounts. Vets generally sort it into two groups:

• Acute diarrhea starts suddenly and typically lasts a few days at most.
• Chronic diarrhea lasts two weeks or longer, or keeps coming back. It almost always deserves a vet visit, even if your cat seems otherwise well.

It also helps to note where the problem seems to come from. Small bowel diarrhea tends to be large in volume with weight loss. Large bowel diarrhea tends to be small, frequent and urgent, often with mucus or a streak of fresh blood.

Common Causes

• Diet changes and dietary indiscretion. A sudden switch of food, a new treat, table scraps or a raid on the bin are classic triggers. Switching food gradually over about a week helps prevent this.
• Intestinal parasites. Roundworms, Giardia, coccidia and others are especially common in kittens and cats with outdoor access. A single fecal test can miss parasites, so vets sometimes repeat it.
• Stress. Moving house, a new pet or a boarding stay can upset a cat's gut.
• Infections. Bacterial and viral infections can cause diarrhea, often with vomiting or fever.
• Food intolerance or allergy. Some cats react to particular proteins or ingredients.
• Foreign objects and toxins. String, hair ties and certain plants or foods can cause serious trouble.
• Chronic disease. Inflammatory bowel disease, hyperthyroidism, kidney or liver disease, pancreatitis and intestinal lymphoma can all show up as ongoing loose stool.

What the Stool Tells You

• Soft but formed, otherwise normal cat: often diet-related and mild.
• Watery and frequent: raises the risk of dehydration, especially in kittens and seniors.
• Mucus or a streak of bright red blood: points to the large bowel; mention it to your vet.
• Black, tarry stool: can mean digested blood from higher in the gut and warrants prompt veterinary attention.
• Worms or rice-like segments: parasites. Bring a sample.

A vet from Ask Vetster explains the red flags that separate mild diarrhea from serious illness.

What You Can Do at Home

For a bright, alert adult cat that is eating, drinking and acting normally, with mild diarrhea that has lasted less than a day or so, vets commonly suggest the following:

• Keep fresh water available everywhere, and consider adding a little water to wet food to boost fluid intake.
• Offer small, frequent portions of a bland, easily digestible diet for a day or two if your vet agrees. Do not fast a cat for long: cats that stop eating can develop liver problems.
• Return to normal food gradually over several days.
• Keep the litter box spotless so you can track how often your cat goes and what the stool looks like.
• Take a photo and note the date. It helps your vet far more than a description.

Never give human medicines. Pepto-Bismol contains a salicylate relative of aspirin that is dangerous to cats, and other anti-diarrheal products can be harmful or mask a problem. Probiotics made for cats are sometimes recommended, but ask your vet which one.

Dr. Alicia explains how to judge whether your cat's diarrhea is an emergency and what to do next.

Check for Dehydration

Diarrhea drains fluid fast. Signs include tacky or dry gums, sunken eyes, lethargy and skin that slowly settles after a gentle pinch. The skin test is unreliable in thin, elderly or overweight cats, so treat it as one clue rather than a verdict. A cat that looks dehydrated needs a vet the same day.

When to See the Vet

Do not wait if you notice any of the following:

• Diarrhea lasting more than 24 to 48 hours, or coming back repeatedly
• Vomiting alongside the diarrhea
• Blood, black tarry stool or visible worms
• Lethargy, hiding, a painful or swollen belly, or refusal to eat
• Signs of dehydration
• Any diarrhea in a kitten, a senior cat, or a cat with a known illness such as kidney disease or diabetes
• Possible exposure to a toxin or a swallowed foreign object

Expect your vet to ask about diet, treats, outdoor access and recent changes. They may recommend a fecal test, blood work, imaging or a diet trial. Chronic cases are often solved by finding the underlying cause rather than treating the stool itself.

Preventing the Next Episode

• Introduce new foods slowly, mixing them in over seven to ten days.
• Keep deworming and parasite prevention up to date.
• Limit table scraps and keep toxic foods and plants out of reach.
• Reduce stress with predictable routines, hiding places and gradual introductions to new pets.
• Pick up string, ribbon and hair ties.

The Bottom Line

One loose stool in an otherwise happy cat is rarely cause for alarm. Persistent, bloody or watery diarrhea, or any diarrhea in a very young, old or sick cat, is worth a call. When in doubt, ask: a short phone conversation costs far less than a dehydrated cat.

This article is general information, not veterinary advice. If you are worried about your cat's health, contact your vet.