Supplement analysis backed by scientific evidence · PT · ES · DE · FR

← All supplements
Moderate evidenceGut health

Saccharomyces Boulardii

A probiotic yeast with genuinely good evidence for preventing antibiotic-associated diarrhoea and reducing the side effects of H. pylori eradication. Because it is a yeast, it survives antibiotics — but it can cause fungaemia in critically ill and catheterised patients, which is a real, documented risk.

View on iHerb Ships to 180+ countries · welcome discount for new customers

What the science says

  • Prevents antibiotic-associated diarrhoea Strong evidence

    A systematic review with meta-analysis of 21 RCTs (n≈4,780) found S. boulardii reduced the risk of antibiotic-associated diarrhoea from about 18.7% to 8.5% (RR ~0.47), in both children and adults. This is one of the better-supported probiotic indications, and the effect is strain-specific to S. boulardii CNCM I-745.

  • Improves tolerance of H. pylori eradication therapy Moderate evidence

    A meta-analysis of 18 RCTs found adding S. boulardii to standard eradication regimens modestly raised eradication rates (RR ~1.11) and clearly reduced overall therapy-related adverse effects, particularly diarrhoea (RR ~0.51). The symptom benefit is more convincing than the eradication benefit.

  • Treats acute infectious diarrhoea in children Moderate evidence

    Pooled trials show S. boulardii shortens acute gastroenteritis by roughly 24 hours and reduces stool frequency, though trial quality is variable and most data come from settings without routine rotavirus vaccination. Benefit is smaller in vaccinated, well-nourished populations.

  • Prevents C. difficile infection recurrence Limited evidence

    Despite widespread marketing, evidence for preventing primary or recurrent C. difficile infection is inconsistent — some trials show benefit in recurrent disease when combined with high-dose vancomycin, but pooled results are not robust enough to recommend it for this purpose.

Dosage & safety

Studied dose250-500 mg twice daily (roughly 5-10 billion CFU/day; 1 g of the lyophilised preparation ≈ 2×10^10 CFU). For antibiotic-associated diarrhoea, start with the antibiotic and continue for at least a week after finishing. Unlike bacterial probiotics it is not killed by antibiotics, so it can be taken at the same time.
SafetyThe important risk is fungaemia: dozens of cases of S. boulardii bloodstream infection are documented, almost all in critically ill, immunocompromised or central-venous-catheter patients, including some acquired from opening capsules near a catheter. Contraindicated in ICU patients, the immunosuppressed, those with central lines, and anyone with a yeast allergy. It is a live yeast, so avoid combining with systemic antifungals (which inactivate it). Commonly causes mild gas, bloating, thirst and constipation. Not a substitute for antibiotics in C. difficile infection. Regulatory status varies — it is a licensed medicine (Florastor, Ultra-Levure, Enterol) in parts of Europe and Asia but sold as a dietary supplement in the US.

How to take it

TimingStart it with the first antibiotic dose and keep going for at least a week after the course ends.
With food?With or without food, but with a cool drink — heat kills the yeast.
Worth knowingUnlike bacterial probiotics it survives antibiotics, so there is no need to space the doses; do avoid opening capsules near a central line, as airborne contamination has caused infections.

Interactions

With medications

  • systemic antifungals (fluconazole, itraconazole, amphotericin B, nystatin)

    S. boulardii is a live yeast and antifungal drugs kill it, so the probiotic does nothing. do not take them together; wait until the antifungal course is finished

  • immunosuppressants and chemotherapy

    Immunosuppression is the main risk factor in the documented cases of S. boulardii fungaemia. do not use while immunosuppressed without medical supervision

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does Saccharomyces boulardii prevent antibiotic diarrhea?

Yes — Saccharomyces boulardii has strong evidence: a meta-analysis of 21 trials found it cut antibiotic-associated diarrhoea from about 18.7% to 8.5%, in children and adults. The effect is specific to the CNCM I-745 strain.

Can I take Saccharomyces boulardii at the same time as antibiotics?

Yes. Saccharomyces boulardii is a yeast, so antibiotics do not kill it and there is no need to space doses. Start with the first antibiotic dose and continue for at least a week after the course ends.

How much Saccharomyces boulardii per day?

The usual Saccharomyces boulardii dose is 250-500 mg twice daily, roughly 5-10 billion CFU/day. Take it with a cool drink, since heat kills the yeast.

Who should not take Saccharomyces boulardii?

Avoid Saccharomyces boulardii if you are critically ill, immunosuppressed, have a central line or a yeast allergy, because it can cause fungaemia (bloodstream yeast infection). Do not take it with systemic antifungals, which kill it.

Scientific references

Where to buy

NOW Foods, Saccharomyces Boulardii, Probiotic , 5 Billion CFU, 60 Veg Capsules

View on iHerb

Ships to 180+ countries · welcome discount for new customers

Referral link — this site may earn a commission on purchases.

Related in Gut health