Saccharomyces Boulardii: what it does and who it's for

Want a simple, natural tool to manage diarrhea or support gut health during antibiotics? Saccharomyces boulardii is a probiotic yeast used for years to shorten diarrhea, lower risk of antibiotic-associated diarrhea, and help with some gut infections. It’s not a miracle cure, but it’s one of the better-studied probiotics out there.

How it works and when to use it

S. boulardii works differently than bacterial probiotics. It survives stomach acid, stays active in the gut for a short time, and helps block harmful microbes while supporting the gut lining and immune response. That makes it useful for:

- Antibiotic-associated diarrhea: taking S. boulardii alongside antibiotics can reduce the chance of getting diarrhea.
- Infectious diarrhea: it can shorten symptom duration for some cases of traveler’s diarrhea and viral or bacterial diarrhea.
- Clostridioides difficile (C. diff): evidence shows it can help lower recurrence risk when used with standard treatment in some patients.

People also try it for IBS symptoms and small intestinal bacterial overgrowth (SIBO), but evidence there is mixed. If you have chronic gut issues, talk to your clinician before starting it.

Dosage, safety, and choosing a product

Common doses fall between 250 mg and 500 mg once or twice daily, depending on product strength. Many brands list doses in CFU (colony-forming units); typical ranges are 5–10 billion CFU per day. A practical approach is: start with the manufacturer’s recommended dose and follow your doctor’s advice for special situations.

Safety: most people tolerate S. boulardii well. Mild side effects can include gas, bloating, or constipation. Avoid it if you are severely immunocompromised, have a central venous catheter, or are critically ill — rare cases of fungemia (yeast in the blood) have been reported in those groups.

Drug interactions are limited. Antifungal drugs could reduce its effectiveness, since they target fungi. If you take prescription antifungals, check with your provider before using S. boulardii.

Picking a product: look for a named strain (for example, S. boulardii CNCM I-745 is common in studies), clear CFU labeling, and a recent expiry date. Third-party testing and a reliable manufacturer help too. Storage instructions vary — some formulations are shelf-stable, others recommend refrigeration. Follow the label.

Practical tips: take S. boulardii during the course of antibiotics and for about one week after to reduce antibiotic-associated diarrhea risk. If using for traveler’s diarrhea, start a few days before travel when possible and continue while you’re away. Stop and contact your doctor if you get fever, worsening symptoms, or signs of infection.

If you’re unsure whether S. boulardii is right for you, ask a pharmacist or your healthcare provider. They can help match strain, dose, and timing to your needs and medical history.