Evidence explainerProbiotics

Probiotics With Antibiotics: Two Strains Have the Data, and Strain Is Everything

Pooled trials found Saccharomyces boulardii and Lactobacillus rhamnosus GG lowered the risk of diarrhea during antibiotic courses. That result belongs to those strains, not to probiotics in general.

By Kymata Health editorial teamPublished October 9, 2026Last reviewed October 9, 2026

Medical review pending. Written by our editorial team from the studies cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • Across 21 trials (4,780 people), Saccharomyces boulardii lowered antibiotic-associated diarrhea from 18.7% to 8.5% [1].
  • Across 11 trials (1,308 people), LGG lowered it from 22.4% to 12.3%, with low-quality evidence; the reduction was significant in children but not adults overall [2].
  • ODS says starting LGG or S. boulardii within 2 days of the first antibiotic dose lowered risk, with no evidence that multiple strains work better [3].
  • Bloodstream infections linked to probiotics have occurred mostly in severely ill or immunocompromised people [3].

The evidence, graded

Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.

  • Grade AWorsenedDiarrhea risk during antibiotic treatmentProbiotics · Meta-analysis · n=4,780 · 2015 · PMID 26216624Antibiotic-associated diarrhea fell from 18.7% to 8.5% (RR 0.47; number needed to treat 10): in children from 20.9% to 8.8%, in adults from 17.4% to 8.2%. C. difficile-associated diarrhea fell significantly in children only.
  • Grade BWorsenedDiarrhea risk during antibiotic treatmentProbiotics · Meta-analysis · n=1,308 · 2015 · PMID 26365389Antibiotic-associated diarrhea fell from 22.4% to 12.3% (RR 0.49; low quality of evidence). Separately, the reduction was significant in children (5 RCTs, n=445) but not in adults (6 RCTs, n=863), except in a subset on H. pylori eradication therapy.

Saccharomyces boulardii

A 2015 meta-analysis of 21 randomized trials (4,780 children and adults taking antibiotics) found S. boulardii lowered antibiotic-associated diarrhea from 18.7% to 8.5% (relative risk 0.47) [1]. The drop was from 20.9% to 8.8% in children and from 17.4% to 8.2% in adults [1].

Lactobacillus rhamnosus GG

A 2015 meta-analysis of 11 trials (1,308 people) found LGG lowered antibiotic-associated diarrhea from 22.4% to 12.3% (relative risk 0.49), rated low-quality evidence [2]. The reduction was significant in children (5 trials) but not in adults (6 trials), except in a subset on H. pylori eradication therapy [2].

Why strain matters

ODS says probiotic effects can be strain-specific, so findings for one strain do not carry over to another [3]. It reports that starting LGG or S. boulardii within 2 days of the first antibiotic dose reduced risk in children and adults aged 18 to 64, with no evidence that multiple-strain products work better [3].

To check what a product contains, see how to read a probiotic label.

Who should be careful

Serious bloodstream infections linked to probiotics have occurred mostly in severely ill or immunocompromised people, and many Saccharomyces cases involved intensive care, central lines or tube feeding [3]. FDA has warned that hospitalized preterm infants given probiotic products are at risk of invasive, potentially fatal infection [4].

Quick answers

When should a probiotic be started with antibiotics?

ODS reports that starting LGG or S. boulardii within 2 days of the first antibiotic dose reduced risk [3].

Does any probiotic work with antibiotics?

The pooled results are strain-specific: S. boulardii and LGG [1][2]. ODS says effects for one strain cannot be assumed for others [3].

Are multi-strain probiotics better with antibiotics?

ODS found no evidence that multiple strains work better than LGG or S. boulardii alone [3].

Keep reading

Full monographs

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References

  1. [1]Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Aliment Pharmacol Ther, 2015. PMID 26216624
  2. [2]Systematic review with meta-analysis: Lactobacillus rhamnosus GG in the prevention of antibiotic-associated diarrhoea in children and adults. Aliment Pharmacol Ther, 2015. PMID 26365389
  3. [3]Probiotics: Fact Sheet for Health Professionals (Updated March 25, 2025). NIH Office of Dietary Supplements, 2025.
  4. [4]FDA Raises Concerns About Probiotic Products Sold for Use in Hospitalized Preterm Infants (October 26, 2023). U.S. Food and Drug Administration, 2023.

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