Saccharomyces boulardii
Useful mainly for people on antibiotics or with acute diarrhea.
Quick decision guide
May help most
people on antibiotics or with acute diarrhea
Common dosing range
500-1000 mg/day (5-20 billion CFU)
When to expect effects
Days
Watch out for
do not use if immunocompromised or with a central venous catheter (fungemia risk)
What is it
Saccharomyces boulardii is a beneficial yeast strain related to baker's yeast (S. cerevisiae) but with distinct properties. It is among the most extensively studied probiotic organisms and is widely used for prevention and treatment of various forms of diarrhea.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
antibiotic-associated diarrhea prevention Strong Evidence | Roughly halves incidence in pooled trials | Adults and children taking antibiotics | Days |
acute infectious diarrhea Good Evidence | Shortens duration by ~1 day | Adults and children with acute gastroenteritis, alongside rehydration | Days |
H. pylori eradication (adjunct) Good Evidence | Improves tolerability; small eradication gain | Patients undergoing H. pylori triple/quadruple therapy | Days to weeks |
Clostridioides difficile infection prevention Limited Evidence | Modest risk reduction | Higher-risk patients on antibiotics, as an adjunct | Days |
traveler's diarrhea prevention Limited Evidence | Modest | Travelers to higher-risk regions | Days |
antibiotic-associated diarrhea prevention
- Effect
- Roughly halves incidence in pooled trials
- Best fit
- Adults and children taking antibiotics
- Time
- Days
acute infectious diarrhea
- Effect
- Shortens duration by ~1 day
- Best fit
- Adults and children with acute gastroenteritis, alongside rehydration
- Time
- Days
H. pylori eradication (adjunct)
- Effect
- Improves tolerability; small eradication gain
- Best fit
- Patients undergoing H. pylori triple/quadruple therapy
- Time
- Days to weeks
Clostridioides difficile infection prevention
- Effect
- Modest risk reduction
- Best fit
- Higher-risk patients on antibiotics, as an adjunct
- Time
- Days
traveler's diarrhea prevention
- Effect
- Modest
- Best fit
- Travelers to higher-risk regions
- Time
- Days
Evidence for 5 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
antibiotic-associated diarrhea prevention
Disease adjunctAs a yeast, S. boulardii is unaffected by antibiotics and can be taken concurrently. Consistent meta-analyses of RCTs show it reduces the incidence of antibiotic-associated diarrhea, supporting its use as a preventive adjunct during antibiotic therapy.
Bottom line: One of the best-evidenced probiotics for preventing antibiotic-associated diarrhea.
acute infectious diarrhea
Disease adjunctMeta-analyses of RCTs show S. boulardii shortens the duration of acute infectious diarrhea, including in children, by binding pathogen toxins, blocking pathogen attachment, and supporting the gut barrier. It is an adjunct to, not a replacement for, rehydration.
Bottom line: Reliably shortens acute diarrhea by about a day as an adjunct to rehydration.
H. pylori eradication (adjunct)
Disease adjunctAdded to standard H. pylori regimens, S. boulardii reduces therapy-related side effects (especially diarrhea) and modestly improves eradication rates in meta-analyses. It is an adjunct to antibiotic eradication therapy.
Bottom line: A useful adjunct that improves tolerability of H. pylori eradication therapy.
Clostridioides difficile infection prevention
Disease adjunctS. boulardii binds and neutralizes C. difficile toxins A and B, and trials suggest it may reduce recurrence or incidence as an adjunct to standard therapy. Evidence is positive but less consistent than for general antibiotic-associated diarrhea.
Bottom line: May help prevent C. difficile-associated disease as an adjunct, with moderate evidence.
traveler's diarrhea prevention
Disease adjunctSome RCTs report a modest reduction in traveler's diarrhea incidence with prophylactic S. boulardii. Effect sizes vary with destination and dose.
Bottom line: A reasonable, modest-benefit option for traveler's diarrhea prevention.
How it works
How to take it
What to track
3 commercial forms
Compare the main delivery options and what they’re best suited for.
Saccharomyces boulardii CNCM I-745 (Florastor brand)
Used in many positive clinical trials. Considered the reference strain.
Most extensively studied strain in clinical research.
Generic S. boulardii capsules
Less expensive option. Look for products with verified CFU counts and reputable manufacturing.
Various strains; quality and viability vary.
S. boulardii powder (pediatric or feeding tube use)
Commonly used in pediatric and clinical settings.
Easily mixed into liquids; useful for children.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Serious risks
Fungemia or fungal sepsis in immunocompromised, catheterized, or critically ill patients
Who should avoid it
- Immunocompromised people
- People with central venous catheters
- Critically ill patients
- People taking antifungal drugs
Pregnancy & breastfeeding
Safety data in pregnancy and breastfeeding are limited; consult a clinician.
Interactions
Drugs like fluconazole or nystatin kill the yeast, negating its effect
No reduction in viability; can be co-administered, unlike bacterial probiotics
Documented interactions
Evidence-graded pair pages with sources, dosing notes, and timing guidance — a complement to the narrative section above.
See all 1 Saccharomyces boulardii interaction →Protocols featuring Saccharomyces boulardii
Evidence-backed routines where Saccharomyces boulardii plays a role.
Antibiotic Recovery
detox
Antibiotics save lives. They also flatten the gut microbiome — even a single short course measurably reduces bacterial diversity for weeks to months, and the most affected taxa can stay altered out to six months. Broad-spectrum agents (clindamycin, fluoroquinolones, broad-spectrum cephalosporins) cause the deepest disruption and carry the highest risk of Clostridioides difficile colitis. Repeated courses — common in childhood, in immunocompromised adults, and in recurrent UTI / sinusitis / bronchitis patterns — have cumulative effects on diversity, immune signalling, and metabolic health. This protocol is for adults DURING and AFTER a prescribed antibiotic course. It is not a replacement for the antibiotic, and it is not an excuse to push for antibiotics that aren't needed. The goal is narrower: reduce antibiotic-associated diarrhea, reduce the risk of C. difficile colonization, and shorten the time your gut microbiome spends in a disrupted state.
Daily Gut Foundation
digestion
The gut-supplement market is overrun with "leaky gut" cure-alls and proprietary blends. The actual evidence is narrower than the marketing suggests. What is well-supported: a diverse fiber intake feeds beneficial bacteria, specific probiotic strains reduce antibiotic-associated diarrhea and shorten gastroenteritis episodes, and L-glutamine has some evidence for intestinal barrier support. This protocol is the conservative foundation — start here before chasing specific gut conditions with more aggressive interventions.
Food sources
| Food | Amount | %DV |
|---|---|---|
| Tropical fruits (lychee, mangosteen) — original isolation | N/A | — |
Tropical fruits (lychee, mangosteen) — original isolation
- Amount
- N/A
- %DV
- —
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
Is S. boulardii a bacterium?⌄
No, it is a yeast. This is why it is not affected by antibiotics, unlike bacterial probiotics. It can be taken simultaneously with antibiotics.
Can I take it during antibiotic therapy?⌄
Yes. Unlike bacterial probiotics, S. boulardii is not killed by antibiotics. Start at the beginning of antibiotic therapy and continue for at least several days to a week after finishing antibiotics.
Is it safe for immunocompromised people?⌄
Generally no. Immunocompromised individuals, those with central venous catheters, and critically ill patients should avoid S. boulardii due to rare but serious risk of fungal infections.
What dose should I take?⌄
Typical adult doses are 250 to 500 mg one to four times daily. Higher doses are used during active diarrhea or antibiotic therapy; lower doses for prevention. Follow product directions.
How long can I take it?⌄
Short-term use (days to weeks) is well established. Longer-term use beyond a few months has less data but no specific safety concerns have emerged in healthy people.
References by claim
Track Saccharomyces boulardii with Pilora
Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.
Coming to App StoreDisclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.