What Causes Cat Diarrhea and What to Do About It

Heather Newett, MPH, DVM
By Heather Newett, MPH, DVM on Jan. 28, 2021
cat lying and looking sad on a windowsill


Our feline friends hide disease and injury incredibly well, so cat parents should be aware of subtle signs of illness. As a cat parent, you need to pay attention to your cat’s circadian rhythms, energy levels, eating and drinking interest, and urination and defecation habits.

When it comes to defecation, consistency, color, and frequency are factors that you should pay close attention to—even if it feels slightly awkward to bring up, your veterinarian wants to hear about your pet’s poop!

And if your cat has diarrhea, you should definitely take notice. Here’s what you need to know about diarrhea in cats.

Is Cat Diarrhea Normal or Serious?

Diarrhea in cats is a common symptom of many diseases, and it is never normal. The causes range from harmless to deadly.

Kittens, senior cats, cats with chronic disease, and pregnant cats are all at increased risk of death-related to complications from untreated diarrhea.

If diarrhea is not self-resolving within a 24-hour period, especially in these populations, you should seek out veterinary care.

Stool consistency suggests the degree of severity to your veterinarian. Liquid diarrhea is concerning because it dehydrates and malnourishes an animal quickly. Soft, formed stool is generally less severe but should still be assessed by a veterinarian.

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What Causes Diarrhea in Cats?

Cat diarrhea can be acute or chronic, and there are different sets of possible causes for each.

Acute means that the diarrhea just happened suddenly or doesn’t go on for long period of time. Chronic diarrhea is characterized as lasting for two to three weeks or longer.

Acute Diarrhea in Cats

There are six main categories when it comes to the cause of acute diarrhea in cats:

  • Infectious (parasitic, protozoal, bacterial, fungal, or viral)

  • Inflammatory (such as food allergies)

  • Metabolic or endocrine (such as diabetes or hyperthyroidism)

  • Cancerous

  • Obstructive

  • Poisonous/toxic

Treats or sudden diet changes can also cause diarrhea in cats. It is important to make sure that the products that you feed to your cat are carefully inspected and introduced slowly.

Treats or new foods (canned or dry) can cause diarrhea if they are contaminated, are suddenly introduced, contain ingredients that are toxic to cats, or contain ingredients that cats are allergic to.

Chronic Diarrhea in Cats

Causes of chronic diarrhea include:

  • Resistant infections

  • Chronic inflammatory disease

  • Poorly managed metabolic or endocrine disease

  • Congenital disease

  • Cancer

Chronic diarrhea is of particular concern because it can cause life-threatening complications. Long-lasting diarrhea that is resistant to treatment can often be multifactorial, with multiple treatments needed for complete resolution.

If no improvement is seen in your cat’s diarrhea within two to three days of initiating therapy, you should contact your veterinarian to check for potential complicating factors.

Red or Bloody Diarrhea in Cats

Bloody diarrhea is always concerning and should be addressed by a veterinarian as soon as possible.

Dark red or black discoloration of feces indicates upper GI bleeding and blood digestion.

Bright red coloration within the feces or coating the feces is a sign of lower intestinal tract bleeding.

Mucus-coated feces indicates possible dehydration or parasitic infection.

Yellow or Green Diarrhea in Cats

Discolored feces can sometimes be related to something your cat has recently ingested. For example, grass or green-colored material may cause green discoloration, which is not always a medical concern, although some animals with green feces have gallbladder disease.

Yellow feces can be an emergency related to liver disease or failure, zinc poisoning, immune-mediated hemolytic anemia, or an overgrowth of certain bacterial pathogens.

What Tests Will My Vet Do to Find the Cause of My Cat’s Diarrhea?

Your veterinarian may run fecal tests that include fecal flotation, antigen testing, cytology, and culturing to screen for infectious or inflammatory disease.

Bloodwork evaluates for metabolic or systemic causes of diarrhea and assesses the consequences of cat diarrhea, such as dehydration or anemia.

Abdominal ultrasound, radiology, and endoscopy can be used to check for foreign body ingestion or cancer as causes of cat diarrhea.

What If My Cat Is Vomiting and Has Diarrhea?

Vomiting in conjunction with diarrhea is always an emergency that must be addressed by a veterinarian.

With or without diarrhea, vomiting suggests potentially life-threatening disorders such as:

What’s the Treatment for Diarrhea in Cats?

Do not try to use Pepto-Bismol, Kaopectate, or any other human medications to treat your cat’s diarrhea, because they can severely harm pets.

If your cat’s diarrhea is yellow, bloody, chronic, coated in mucus, or accompanied by vomiting, contact your vet right away for treatment. You should also call your vet if you have a kitten, senior cat, a cat with a chronic disease, or a pregnant cat that has diarrhea for vet treatment. They can then diagnose the cause and start the related treatment for that cause.

Otherwise, you can increase fiber consumption to treat soft stool at home. You can ask your veterinarian about the frequency and dosing of canned pumpkin or fiber supplements, and there are some feline-specific over-the-counter fiber products that you can get to increase dietary fiber as well.

Feline-specific probiotics can also benefit some cats with diarrhea.

If fiber or probiotic formulations are not enough to return your cat’s stool to its normal consistency after one to two days, consult your veterinarian.

Gradual transition of your cat to an over-the-counter diet targeting gastrointestinal health may provide some benefit, but prescription diets are recommended if diarrhea persists.

Can You Prevent Cat Diarrhea?

Preventing feline diarrhea is possible.

Control underlying diseases such as pancreatitis, irritable bowel syndrome, hyperthyroidism, or food allergies with appropriate medications and prescription diets, as recommended by your veterinarian.

Do not make sudden diet changes or give your cat human foods or rich or novel treats to avoid cases of acute diarrhea.

Your veterinarian is your best resource for treating this complicated and potentially deadly issue.


“Enterocolitis, Acute”. Last updated on 1/7/2020. Contributors: Kari Rothrock DVM https://www.vin.com/Members/Associate/Associate.plx?DiseaseId=5999.

“Managing Toxicoses in Exotic Animals”. March 8, 2020 (published). Tina Wismer, DVM, MS, DABVT, DABT. https://www.vin.com/doc/?id=9547705&pid=25043.


Heather Newett, MPH, DVM


Heather Newett, MPH, DVM


Heather is a practicing small animal veterinarian in Denver, CO. In her free time she enjoys hiking, horseback riding, and traveling to new...

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