✓ No active regulatory warningsFDA MedWatch, EMA EudraVigilance, WHO VigiBase, WADA Prohibited List · 2026-05-29
📰Read the full S. boulardii evidence review on GMJ News →Complete clinical article, references and updates on news.gmj.ge. This page is the structured safety summary.⚠ Can take WITH antibiotics simultaneously — unique yeast advantage [2]
⚠ C. difficile prevention — the strongest probiotic evidence for this indication [2]
⚠ Do NOT co-administer with antifungals (fluconazole kills it) [1]
⚠ ICU patient with CVC — do NOT open S. boulardii capsules at bedside (fungemia from airborne yeast) [1]
ℹ️ Not obtained from food. Not applicable — this is not obtained from food in meaningful amounts; supplementation is the practical route.
🔬 Lab interpreter
ℹ️ No validated blood test. There is no established laboratory test to assess status or guide dosing for this ingredient. Clinical response and symptoms are the practical guide.
⚕ For professionals — confirm ranges against your local laboratory.
Clinical verdict
S. boulardii is the only probiotic UNAFFECTED by antibiotics (it's a yeast). Best evidence: C. difficile prevention and AAD (NNT=10). Can be taken AT THE SAME TIME as antibiotics. Florastor (CNCM I-745) is the original strain. Do NOT give with antifungals (which kill it). Avoid opening capsules near CVCs in ICU patients (fungemia risk) [1] [2].
1 How much do I need?
👤 Adults: Specific dosage data under clinical review
👴 Elderly: Specific dosage data under clinical review
🤰 Pregnancy: See guidance
Generally safe. Transient gut passage (does not colonize) [1].
👦 Pediatric: Specific dosage data under clinical review
🏃 Athletes: Standard dose
⚖️ Obesity: Standard dose
Fat-soluble compounds may require dose adjustment in obesity.
🩺 Renal: Consult specialist
Dose adjustment may be needed in renal impairment.
🌱 Vegan: Standard dose
How to take
🍽 Timing: With or without food. BID. Can take AT THE SAME TIME as antibiotics [2].
💊 With food: Any [2].
2 Which form?
| Form | Bioavailability | Vegan | Cost |
|---|---|---|---|
| ['S. boulardii CNCM I-745 (Florastor)', 'preferred', 'The original and most studied strain. 250 mg capsules. Shelf-stable (yeast is hardy) [2].'] | Standard | Check label | |
| ['S. boulardii (generic)', 'common', 'Various manufacturers. Verify strain if possible [1].'] | Standard | Check label |
3 Common questions
Why can S. boulardii be taken with antibiotics? ▼
Because it's a YEAST, not a bacterium. Antibiotics target bacteria, not fungi. This means S. boulardii maintains its viability throughout antibiotic therapy — the key advantage over Lactobacillus/Bifidobacterium for AAD prevention [2].
Can S. boulardii cause infection? ▼
In immunocompetent individuals: essentially zero risk. In critically ill patients with central venous catheters: rare fungemia cases (S. boulardii contaminating catheter hubs from airborne yeast when opened at bedside). Avoid opening capsules near CVCs [1].
Is Florastor the best brand? ▼
Florastor contains S. boulardii CNCM I-745, the original and most studied strain. Most clinical trials used this strain. Generics may use different sub-strains with potentially different characteristics [2].
How long should I take it with antibiotics? ▼
Start on day 1 of antibiotic therapy. Continue throughout and for 7–14 days after antibiotic completion. This duration is supported by meta-analyses [2].
4 Clinical evidence
Strong
C. difficile prevention: meta-analysis showed S. boulardii significantly reduces C. difficile recurrence when co-administered with standard antibiotics [2]. AAD prevention: meta-analysis of 21 RCTs — NNT=10 for AAD prevention (among the strongest probiotic evidence) [2]. Unaffected by antibiotics: yeast is intrinsically resistant to antibacterial agents [2]. Degrades C. diff toxins A and B via secreted proteases [1]. HIGH
Moderate
Acute diarrhea in children: reduces duration by ~1 day [2]. Traveler's diarrhea prevention: some positive trials [2]. H. pylori therapy adjunct: may reduce antibiotic side effects [2]. IBD (UC): some evidence for maintaining remission [2]. MODERATE
Insufficient
5 Safety, toxicity & adverse events
Absolute contraindications
✕ Critically ill, immunocompromised, or central venous catheter in situ — documented risk of fungemia
✕ Known yeast hypersensitivity
Relative
⚠ Pregnancy and lactation — limited data
⚠ Concurrent systemic antifungals — may reduce probiotic effect
🚩 Red flags
● ICU patient with CVC — do NOT open S. boulardii capsules at bedside [1]
● Patient on fluconazole/antifungals — S. boulardii will be killed [1]
● Severely immunocompromised — fungemia risk [1]
6 Interactions
Drug interactions
Antifungal medications (fluconazole, itraconazole) Major
Mechanism: Antifungals kill S. boulardii (it is a yeast). [1]
Effect: Eliminates probiotic effect. [1]
Action: Do not co-administer. S. boulardii and antifungals are fundamentally incompatible [1].
Antibiotics None (advantage)
Mechanism: Antibacterial agents do not affect yeast. [2]
Effect: S. boulardii maintains full viability during antibiotic therapy. [2]
Action: Can be taken simultaneously with any antibiotic — this is the key advantage [2].
Supplement synergies
LGG (Lactobacillus rhamnosus GG) · LGG 10–20 billion CFU/day
Yeast + bacteria = comprehensive AAD prevention. S. boulardii (unaffected by antibiotics) + LGG (separated from antibiotics by 2 hours) [2].
Yeast + bacteria = comprehensive AAD prevention. S. boulardii (unaffected by antibiotics) + LGG (separated from antibiotics by 2 hours) [2].
Prebiotics · 3–5 g/day FOS/inulin
Feed both bacterial and yeast probiotics [1].
Feed both bacterial and yeast probiotics [1].
7 Regulatory
United States (FDA): Dietary supplement. Not FDA-approved as drug [1].
France: Prescription probiotic (Ultra-Levure). Originally developed in France [1].
WHO/WGO: Recommended for AAD and C. difficile prevention in guidelines [2].
South Korea: Dietary supplement.
8 Cite this page
Vancouver: Pkhakadze G. S. boulardii — safety profile [Internet]. Tbilisi: PHIG; 2026 [cited 2026 Aug 15]. Available from: https://supplement.ge/ingredients/s-boulardii/
APA 7th: Pkhakadze, G. (2026). S. boulardii — Safety profile. Public Health Institute of Georgia. https://supplement.ge/ingredients/s-boulardii/
📋 Editorial information
Author: Prof. G. Pkhakadze, MD, MPH, PhD
Institution: Public Health Institute of Georgia (PHIG)
Affiliation: David Tvildiani Medical University (DTMU)
First published: January 2026
Last reviewed: 2026-05-29
Next review: February 2027
References: 2 cited sources
COI: SupplementIndex receives no funding from supplement manufacturers. All content independently authored by PHIG.
Process: Systematic literature review
📄 License & reuse
Published under Creative Commons Attribution 4.0 International (CC BY 4.0). You may share and adapt for any purpose with attribution.
Pkhakadze G. "S. boulardii — Safety Profile." SupplementIndex, PHIG, 2026. https://supplement.ge/ingredients/s-boulardii/ CC BY 4.0.
GP
Prof. G. Pkhakadze, MD, MPH, PhD
Professor of Public Health · Head of Department, DTMU
Editor-in-Chief, Georgian Medical Journal (ISSN 3088-4322)
Chair, Public Health Institute of Georgia · UEMS Public Health Section
Educational and public health purposes. CC BY 4.0. Consult your healthcare provider before starting any supplement. Corrections: info@accreditation.ge. Publisher: PHIG