Diarrhea is one of the top reasons cats are seen by veterinarians. Digestive upset can be triggered by a wide range of factors, so figuring out the true cause of your cat’s diarrhea can be tricky. Here are some of the most common causes of diarrhea in cats:

As obligate carnivores, cats don’t need the longer gastrointestinal tracts required by omnivores like humans, who eat a much broader diet, or herbivores like cows and rabbits, who eat plants. A cat’s digestive tract is relatively short, and a high-protein meal moves through quickly. It typically takes a cat’s food about 20 hours to pass through the whole GI tract, whereas in a human, digestion may take as long as 72 hours. The fast transit rate of food through the feline GI tract reflects its adaptation to a hunting lifestyle, making the cat ready to pounce on the next prey item after quickly digesting its current one.

Different illnesses arise in different parts of the intestinal tract, so in figuring out the cause of your cat’s problem, it’s helpful to determine whether the diarrhea originates in the small intestine or the large intestine (colon).

For example, because the small intestine is where most nutrients get absorbed, problems here can mean the body is missing out on a lot of the nutrition in your cat’s food, which can create additional problems, like weight loss and nutrient deficiencies. Your cat’s poop can offer important clues:

The color of your cat’s poop may also help you figure out what’s going on. This Cat Poop Color Chart describes the most common poop colors and what causes them:

Diarrhea is even more common in kittens than in adult cats. A kitten’s digestive system is still adjusting to solid food, and even small dietary changes can cause intestinal upset. Kittens are more vulnerable to intestinal parasites and pathogens because their immune systems are still developing. They are also more likely to ingest things that might be toxic or could create intestinal blockages. And certain diseases that cause diarrhea are more common in kittens, such as feline enteric coronavirus (FeCoV) and FIP.

Because kittens are small, diarrhea can quickly lead to severe dehydration and weakness. So if your kitten has diarrhea that lasts for more than two days or that is accompanied by other symptoms, contact your veterinarian right away.

With an adult cat, a loose stool in the litter box from time to time isn’t cause for concern. And if your cat is otherwise behaving normally and seems to feel fine, it’s reasonable to wait a day or two to see if the diarrhea will resolve on its own.

But if your cat’s diarrhea lasts longer than two days (and longer than one day for a kitten) or is accompanied by additional clinical signs—such as vomiting, poor appetite, or lethargy—it could indicate a serious health issue. And if you think your cat might have ingested something poisonous or swallowed a foreign object, you should seek veterinary care immediately.

Your veterinarian may use a number of diagnostic approaches in investigating the possible causes of your cat’s diarrhea, including a physical exam, fecal parasite/pathogen test, blood work, urinalysis, and imaging (such as x-ray or ultrasound).

Avoid medications unless prescribed by your vet. Never give your cat any human anti-diarrheal medication, since many of these products are toxic or fatal to cats. Avoid antibiotics unless they’re absolutely necessary, since most antibiotics can worsen or cause diarrhea. If your cat has a bacterial infection and your veterinarian determines that antibiotics are necessary, it’s important to support your cat’s gut health during and after the course of medication.

Feed the right diet. Check with your veterinarian before making any changes to your cat’s diet. If your cat’s usual food is high in carbohydrates, ask about gradually adding more protein. Make sure you’re feeding a high-quality, cat-appropriate diet. It’s probably best to eliminate treats and any other extras until the diarrhea has been resolved. And always provide your cat with plenty of fresh water.

Don’t withhold food. Fasting your cat for a few hours is often recommended for vomiting, but it’s unlikely to help diarrhea. (Never withhold food from a cat for any reason for more than 24 hours; insufficient nutrition over just a few days can lead to a potentially fatal liver condition in cats.)

Add fiber and prebiotics. Adding certain sources of fiber to your cat’s food—particularly the prebiotic fibers inulin and psyllium—can improve diarrhea both by absorbing excess water in the intestines and by providing food for beneficial bacteria that live in the intestinal tract. Always start with a very small amount of any fiber.

Especially if your cat’s diarrhea is a result of a course of antibiotics or an overgrowth of E. coli, Gut Maintenance Plus (GMP) for cats can help. Containing the probiotic yeast Saccharomyces boulardii, the prebiotic MOS, and a bacteriophage cocktail called PreforPro®, our GMP product was specifically designed to resolve diarrhea caused by antibiotics or E. coli.

Studies have shown that S. boulardii is safe and effective for preventing and reducing diarrhea from multiple causes, including antibiotic usage. As a probiotic, it’s especially helpful for regrowing gut microbe populations that have become imbalanced.

S. boulardii is also included in our KittyBiome S. boulardii + FOS Powder. “FOS” stands for fructo-oligosaccharides, which are tiny, soluble fibers that have been shown to improve gut health when added to a cat’s diet. Research has found that FOS offers greater benefits for cats than other prebiotic fibers, and there’s even evidence that adding FOS to a cat’s diet leads to a decrease in harmful E. coli bacteria.

Test your cat’s gut health. Gut microbiome testing can tell you a lot about what’s going on in your cat’s digestive system and how to correct certain problems. By identifying all the different kinds of bacteria in your cat’s gut, our easy, noninvasive Gut Health Test can determine whether those bacterial populations are present in balanced amounts when compared to the gut microbiomes of healthy cats.

Like humans, cats depend on the bacteria that live in the GI tract to help digest their food and extract its nutrients. A diverse, well-balanced gut microbiome also supports the immune system, keeps your cat’s coat healthy, and even promotes a happy mood. But when some beneficial bacteria populations go missing, the microbiome becomes imbalanced, and important digestive and immune functions may no longer work properly. The earlier you can catch an imbalance with microbiome testing, the easier it will be to resolve.

Your cat's microbiome test report will give you customized recommendations on how to best restore and maintain your cat’s gut health. If an imbalance is detected, the report may include dietary recommendations, which often is all that is necessary to adjust the balance among your cat’s resident gut bacteria groups. Transitioning to a higher-protein, lower-carbohydrate diet, for example, may improve your cat’s gut health by encouraging the growth of the important Fusobacteria group, which thrives in a high-protein environment.

For cats with chronic diarrhea caused by more serious microbiome imbalances or IBD, our KittyBiome Gut Restore Supplement can help bring balance to the gut and relieve symptoms. Offering the benefits of fecal transplant in an oral capsule, our Gut Restore Supplements provide the gut with missing beneficial bacteria and crowd out harmful ones by seeding it with an entire community of healthy cat-specific gut microbes.

In animal shelters, cats with diarrhea typically aren’t adopted out as quickly as healthy animals and are therefore more vulnerable to euthanasia. Read Marigold’s story; a shelter cat with chronic diarrhea who found a forever home and a solution to her digestive problems.

Because chronic diarrhea is such a serious problem for cats at animal rescues and shelters, we help support these organizations by offering product discounts and by periodically donating microbiome tests and supplements.

My cat’s poop is mushy but not liquid. Is it still diarrhea?

Can you help me determine if my cat’s diarrhea is because of a food allergy?

I have more than one cat. What are some easy ways to tell which one has diarrhea?