Do Probiotics Help Cats?

Probiotics for cats have some promising but small studies behind them. The best known, a shelter trial in the Journal of Veterinary Internal Medicine, found diarrhea lasting two days or more in 7.4% of cats given a probiotic, against 20.7% on placebo.

Most other cat trials are smaller still. A 2025 review in Veterinary Sciences called for longer, larger studies. We found no source showing that a healthy cat on a complete and balanced food needs a probiotic, so ask your vet before starting one.

What is a probiotic, exactly?

The definition used worldwide comes from the UN's food agency and the World Health Organization, reaffirmed by the International Scientific Association for Probiotics and Prebiotics (ISAPP) in 2014: "live microorganisms which when administered in adequate amounts confer a health benefit on the host."

So three things have to be true. The microbes are alive, there are enough of them, and there is a demonstrated benefit.

You may also see related words on labels. The Merck Veterinary Manual describes prebiotics as compounds that affect the make-up or activity of the gut bacteria, such as inulin and fructo-oligosaccharides, and notes they may increase lactobacilli and bifidobacteria in dogs and cats.

A synbiotic combines a probiotic with a prebiotic. A postbiotic, as ISAPP defined it in 2021, is a "preparation of inanimate microorganisms and/or their components," meaning the microbes have been deliberately inactivated.

What does the research in cats actually show?

The largest study is the shelter trial. Researchers gave 217 cats and 182 dogs either the probiotic Enterococcus faecium SF68 or a placebo, then tracked their stools.

In cats, diarrhea lasting two days or more was significantly less common on the probiotic: 7.4% against 20.7%. The authors called this a possible beneficial effect. The study was funded by a grant from the probiotic's manufacturer.

What about cats on antibiotics?

Two trials looked at this in healthy research cats. In one, 16 cats took the antibiotic clindamycin for three weeks, followed an hour later by a synbiotic or a placebo.

The cats on the synbiotic ate more, and in the first period all of them finished the course, against half on placebo. They vomited less, though that difference was not statistically significant, and stool scores did not change.

The authors still concluded the synbiotic reduced poor appetite and vomiting.

A 2026 study in the Journal of Feline Medicine and Surgery gave 27 research cats amoxicillin-clavulanate for a week, plus SF68 (now renamed Enterococcus lactis) or a placebo for two weeks.

By day 14, a measure of gut bacterial balance in the probiotic group was back near where it started, while the placebo group's was still shifted. Several authors disclose ties to the probiotic's maker, and the cats were followed for only two weeks.

And everything else?

The 2025 Veterinary Sciences review is frank about the gaps. It notes that many cat studies have fewer than 10 cats per group, and that one meta-analysis rated the overall certainty of the evidence as low and inconsistent.

The same review reported minimal adverse effects across the studies it covered.

Why does the strain matter so much?

A probiotic's full name has three parts: genus, species and strain. In Enterococcus lactis SF68, SF68 is the strain.

Merck puts it plainly: the effects of probiotics depend on the dose and on "the precise strain and composition of the mixture fed." A result for one strain may not carry over to another, even within the same species.

Here is a detail worth knowing. In the shelter trial, the same SF68 product that made a difference in cats showed no difference in the dogs, although few dogs in either group had diarrhea to begin with.

Our guide to probiotics for dogs covers the canine research in more detail.

Does a healthy cat need a probiotic?

None of the research above shows that a healthy cat on a complete and balanced diet needs one. The studies looked at shelter cats under stress or research cats on antibiotics, not typical family cats.

Merck notes that the gut bacteria of dogs and cats are generally stable and resist major change. Even when altered, they often revert to their original state.

The Cornell Feline Health Center says vitamin and mineral supplements are usually not necessary with a balanced and complete diet. Our guides to whether cats need vitamins and whether cats need fiber cover those questions.

Probiotics also come up as an add-on for diagnosed gut conditions. Cornell lists probiotics among newer options for feline inflammatory bowel disease, after dietary change and medication. That is a decision for your vet.

Is what's on the label really in the product?

Not always. When researchers tested 25 animal probiotics for the Canadian Veterinary Journal in 2011, only 4 of the 15 products that promised a number of live bacteria actually met it.

Seven of the 22 products that named their bacteria misspelled at least one name. The authors urged owners and vets to look for evidence of quality control.

An earlier test by the same group looked at 19 dog and cat foods advertising probiotics, 6 of them for cats. None contained every organism listed, and 5 had no relevant growth at all.

How to choose one, if you and your vet decide to try

• Look for the full name, down to the strain, so it can be matched to research.
• Check for a stated count of live bacteria and a use-by date, then follow the storage directions.
• Choose a product made for cats, and ask your vet which strains have been studied for your cat's situation.
• Agree how long to try it and what to watch for.

When should I call the vet instead?

A probiotic should never delay a vet visit. Cornell lists vomiting, weight loss, diarrhea, bloody stools, lethargy and decreased appetite as common signs of feline inflammatory bowel disease, and those signs have many other causes too.

Call your vet promptly if your cat has:

• vomiting or diarrhea for more than 24 hours
• bloody, foul-smelling or uncontrollable diarrhea, or thick, black stools
• not eaten or drunk anything for 24 hours
• extreme tiredness, or sudden weight gain or loss

Merck's veterinary manual lists each of these among signs that need a vet. Cats who stop eating need prompt attention, and our guide to a cat not eating explains why.

Questions new cat parents ask

Are probiotics safe for cats?

The 2025 review reported minimal adverse effects in the studies it covered. The label tests above raise questions about product quality, so ask your vet which product to use.

Can I give my cat a human probiotic?

Ask your vet first. Effects are strain specific, and a strain studied in people may never have been studied in cats.

Should my cat take a probiotic with antibiotics?

Ask your vet. Two small trials in healthy research cats found some benefits, including better appetite in one, but they were short, and the vet prescribing the antibiotic should advise on timing.

Is a cat food with added probiotics enough?

In the 2003 study, none of the 19 dog and cat foods claiming probiotics contained every organism on the label. Ask the maker for evidence if you are relying on one.

Are postbiotics the same as probiotics for cats?

No. Under the ISAPP definitions, a probiotic is alive and a postbiotic is inactivated. The research on postbiotics in cats is earlier still.

Sources

• Bybee SN, Scorza AV, Lappin MR. Effect of the probiotic Enterococcus faecium SF68 on presence of diarrhea in cats and dogs housed in an animal shelter. Journal of Veterinary Internal Medicine, 2011
• Stokes JE, Price JM, Whittemore JC. Randomized, Controlled, Crossover Trial of Prevention of Clindamycin-Induced Gastrointestinal Signs Using a Synbiotic in Healthy Research Cats. Journal of Veterinary Internal Medicine, 2017
• Slaughter M, et al. Oral administration of Enterococcus lactis strain SF68 speeds the recovery of amoxicillin-clavulanate-induced dysbiosis in cats. Journal of Feline Medicine and Surgery, 2026
• Sivamaruthi BS, et al. A Review of Probiotic Supplementation and Its Impact on the Health and Well-Being of Domestic Cats. Veterinary Sciences, 2025
• Weese JS, Martin H. Assessment of commercial probiotic bacterial contents and label accuracy. Canadian Veterinary Journal, 2011
• Weese JS, Arroyo L. Bacteriological evaluation of dog and cat diets that claim to contain probiotics. Canadian Veterinary Journal, 2003
• Hill C, et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology, 2014
• Salminen S, et al. The International Scientific Association of Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics. Nature Reviews Gastroenterology & Hepatology, 2021
• Merck Veterinary Manual: Modifying the Intestinal Microbiota in Animals
• Merck Veterinary Manual: When to See a Veterinarian
• Cornell Feline Health Center: Feeding Your Cat
• Cornell Feline Health Center: Inflammatory Bowel Disease

This article is for general information and is not veterinary advice. Talk to your vet about your own cat — they know the animal in front of them.

Choolip products are food supplements, not medicine. They are not intended to diagnose or manage any medical condition. If your cat has been diagnosed with a condition, their diet should be set by your vet.