Do probiotics prevent diarrhea from antibiotics and C. difficile?

What the reviews found

Antibiotics disturb the gut microbes, and up to 30% of patients who take them get diarrhea.^[2]

• All ages. The 2025 Cochrane review pooled 40 studies with 13,419 people. Probiotics may lower the risk by about a third (risk ratio 0.67, low certainty).^[1] A 2012 review of 63 trials with 11,811 people found a similar effect (risk ratio 0.58), and many of its trials did not describe their strains well.^[4]
• Adults. In 42 studies with 11,305 adults, the risk was 37% lower (moderate certainty). Only certain species worked, and studies in people with a low risk of diarrhea showed no difference.^[5]
• Children. In 33 studies with 6352 children, 8% got diarrhea with probiotics and 19% without. Doses of at least 5 billion colony-forming units (CFU, live cells) a day gave 8% against 23%. Lower doses gave 8% against 13%, and this result could be due to chance. Diarrhea also lasted almost one day less.^[6]

Results for single strains

These results apply only to the strain named:

• Saccharomyces boulardii: in 21 trials with 4780 people, diarrhea fell from 20.9% to 8.8% in children and from 17.4% to 8.2% in adults.^[7]
• Lactobacillus rhamnosus GG: in 12 trials with 1499 people, diarrhea fell from 22.4% to 12.3%, but the difference was statistically significant only in children.^[2]
• Limosilactobacillus reuteri DSM 17938: in 654 children taking amoxicillin-clavulanate, 7.9% got diarrhea by day 14, against 16.7% on placebo.^[8]
• Other Lactobacillus strains: some strains and mixes prevented this diarrhea in adults, and others did not.^[9]

No evidence shows a greater benefit from more than one strain.^[2]

Older people

The evidence is less clear after age 65. Probiotics lowered the risk in children and in adults aged 18 to 64, but not in those aged 65 and older.^[2] In the PLACIDE trial, about 3000 hospital patients aged 65 and older took a mix of lactobacilli and bifidobacteria (60 billion organisms a day) or a placebo for 21 days. Diarrhea affected 10.8% and 10.4%.^[3] A later review of 6 trials found a lower rate in older people when probiotics started within 2 days of the antibiotic.^[10]

C. difficile

Clostridioides difficile is a bacterium that can cause severe diarrhea after antibiotics.^[11] In 38 trials with 13,179 people, one case may be prevented for every 65 people who take probiotics (low certainty). Of all the studies in the review, 28 had ties to probiotic companies. Hospital stays were about the same length.^[1] For S. boulardii alone, the effect on C. difficile was statistically significant in children but not in adults.^[7]

When trials started and stopped

Starting within 2 days of the first antibiotic dose worked better than starting later.^[2] One trial continued until 7 days after the last antibiotic dose.^[12]

Probiotics may also have a cost after antibiotics. A 2018 study in people and mice found that a multi-strain probiotic delayed the return of the gut's own microbes, compared with no treatment.^[13]

What expert groups say

A European pediatric society recommends L. rhamnosus GG or S. boulardii for children with risk factors, at doses of at least 5 billion CFU a day.^[2][14] For C. difficile it gives a weaker suggestion, for S. boulardii only.^[14]

Who should be careful

The Cochrane review judged short-term use as likely safe in people on antibiotics who do not have a weak immune system.^[1] People who do should ask a doctor first.^[2] See Are probiotics safe, and who should avoid them? The doses from trials are in the protocol Probiotics for diarrhea from antibiotics.