Probiotic
Saccharomyces boulardii
Also known as: CNCM I-745, Florastor, S. boulardii
Beneficial yeast probiotic that's antibiotic-resistant. Excellent for diarrhea, C. diff, and antibiotic support.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every Saccharomyces boulardii product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | Onnit Total GUT HEALTH (60 ct) | 86 A- | $1.60 |
| 2 | Jarrow Formulas Saccharomyces Boulardii + MOS | 70 B | $0.34 |
| 3 | Thorne Sacro-B™ | 68 B | $0.72 |
| 4 | NOW Foods Saccharomyces Boulardii | 67 B | $0.42 |
| 5 | Allergy Research Group Essential-Biotic Saccharomyces Boulardii | 57 C+ | $1.34 |
Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.
Common questions
How much Saccharomyces boulardii should I take?
The typical range is 250-500 mg (5-10 billion cells) daily. During infection/antibiotics and 2 weeks after
When should I take Saccharomyces boulardii?
During and after antibiotics. Either way.
Which form of Saccharomyces boulardii is best?
Capsules — Shelf-stable.
Is Saccharomyces boulardii safe?
Commonly reported: Gas, Bloating. Serious warnings: Fungemia in immunocompromised with central lines. Safe
Which Saccharomyces boulardii supplement scores highest?
Onnit Total GUT HEALTH (60 ct), at 86/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.
Primary uses
- Diarrhea
- Antibiotic support
- C. diff prevention
What systematic reviews concluded
Outcomes that systematic reviews of Saccharomyces boulardii reached a verdict on: 4 with a benefit, 3 unclear. Each is quoted from a review and linked to it on PubMed. How these were read.
Reviews found a benefit (4)
“significantly higher eradication rates (78.6% to 89.2%) with adjunctive S. boulardii” PMID 41247686 · 5 reviews
“significantly increased H. pylori eradication rates and decreased the adverse effects.” PMID 40251486 · 5 reviews
“A meta-analysis found a significant therapeutic efficacy for S. boulardii in the prevention of antibiotic-associated diarrhea (AAD) (RR = 0.47, 95% CI: 0.35-0.63, P < 0.001).” PMID 20458757
“Lactobacillus-based probiotics and Saccharomyces boulardii decolonize 71% and 77% of pathogens effectively.” PMID 38778521
Not enough to say: traveler's diarrhea prevention; acute infectious diarrhea duration/incidence; clostridium difficile-associated diarrhea prevention.
1 finding from reviews in specific patient groups (such as cancer, pregnancy or surgery) is not shown here.
How it works
- Not killed by antibiotics
- Secretes anti-toxin factors
- Supports gut barrier
Dosage
- Typical range
- 250-500 mg (5-10 billion cells) daily
- Timing
- During and after antibiotics
- With food
- Either way
- Duration
- During infection/antibiotics and 2 weeks after
- Special populations
- Antibiotic users, recurrent C. diff
Forms
- Capsules
Safety
Common side effects
- Gas
- Bloating
Contraindications
- Central venous catheter
- Severe immunocompromise
Products containing Saccharomyces boulardii
Top-scoring supplements in our catalog that list Saccharomyces boulardii on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Known interactions
Evidence notes
Strong evidence for diarrhea prevention
Grade A: Multiple well-designed human trials support the main claims.
Cited research for Saccharomyces boulardii
Clinical studies referenced across Formulate guides that mention saccharomyces boulardii. Each links to the full study page with PubMed source + the guides that cite it.
Related in Probiotic
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.