What Causes Kitten Diarrhea?

CatChannel and CAT FANCY veterinary expert Arnold Plotnick, DVM, explains some common causes of diarrhea in kittens.

Kitten diarrhea is a common problem.  Via Deborah/Flickr
Kitten diarrhea is a common problem. Via Deborah/Flickr


I bought a 9-week-old kitten from a pet store, and he had diarrhea from the start. I took him to the vet with stool samples, and they gave him Drontal for worms. The vet never found anything in the samples but gave me Metronidazole 50mg/ml suspension just in case.

The medicine didn’t help so they put him on Hill’s Prescription Diet i/d and canned pumpkin. When that didn’t work, they put him on Hill’s Prescription Diet d/d and wanted to wait four weeks to see if it helped. A couple of times, his stool was a little bit more formed; I saw some red spots in some stool and I think it was from my kitten but can’t be sure because I have other cats. If this d/d doesn’t help what could be wrong with him and what can I do for him seeing as my vet can’t ever find anything in his stool?


So many kittens at shelters and humane societies are in need of loving homes that I hope you adopt your next cat from them. In my experience, kittens purchased from pet stores are rarely in good health, and problems like chronic kitten diarrhea you describe are not uncommon. Kittens typically have diarrhea from either a parasite problem or a dietary problem. (Click each for more information.)

  • Hookworms and roundworms (both long, white worms that damage the intestines) are common parasites in cats. I doubt that your cat has these, and the Drontal your vet prescribed is effective against hookworms and roundworms and would have treated them.
  • Tritrichomonas is a protozoan parasite that can cause persistent diarrhea in kittens. I think your cat should be tested for this parasite.
  • Giardia is a protozoan parasite that can cause diarrhea in kittens. Metronidazole is usually effective against this parasite (although resistance is becoming more common). Your cat didn’t respond to metronidazole, and I suspect that this is not the problem either. Still, I would have your vet run a giardia ELISA test to be certain. This is a more precise test to detect the presence of giardia.
  • Coccidiosis or coccidia is a common parasitic infection in cats that  can cause watery diarrhea, sometimes with a little blood (possibly the red spots you’re seeing in the stool) in kittens. It is especially common in cats that come from pet stores.

Kitten Health Diagnosis

I suspect your cat has some type of parasitic or infectious diarrhea. It is usually easily detected in a stool sample, however, and the stool samples you submitted came back negative. Still, you might want to discuss with your vet the option of treating this condition, to see if the kitten responds.

We used to use a drug called Albon to treat, which required a 14 day course of treatment, however, there are newer drugs such as Ponazuril that only require one or two doses. Ponazuril is not approved for use in cats, however. It has to be formulated by a compounding formulary into a liquid that is the proper strength.

The best way to diagnose these infectious causes of diarrhea is by a test called a fecal PCR test. This very sensitive test detects minute amounts of DNA from these organisms. Have your vet run this test and prescribe specific treatment based on the test results. If everything tests negative, you may simply have to try a variety of diets until you find one that causes the firmest stool.

Dietary Help

Diet can help counter the effects of diarrhea for cats with food allergies or cats with digestive issues.

  • Hill’s Prescription Diet i/d is a highly digestible diet that is designed for cats with digestive issues. It’s a very nutritious diet and will even support growth in kittens, so a dietary trial with this diet was reasonable.
  • Canned pumpkin adds a little fiber to the food, in the hopes of firming up the stool.
  • Hill’s d/d is a hypoallergenic diet designed for cats with food allergy.

Several kittens in my practice have had chronic diarrhea that tested negative on every test I ran. These kittens simply “outgrew” their diarrhea as they got older, and we never determined the cause of the diarrhea.

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