Saccharomyces boulardii: What It Is, How It Helps, and What You Need to Know

When you hear "probiotic," you probably think of bacteria—but Saccharomyces boulardii, a non-pathogenic yeast used as a probiotic to restore gut balance and fight diarrhea. Also known as S. boulardii, it’s not a bacterium like Lactobacillus. It’s a friendly yeast that survives stomach acid, sticks to the gut lining, and helps crowd out harmful microbes. Unlike most probiotics, it doesn’t colonize your intestines permanently. Instead, it works like a temporary peacekeeper, calming inflammation and boosting your gut’s natural defenses while you’re on antibiotics or recovering from an infection.

This yeast is especially useful when antibiotic side effects wreck your digestion. If you’ve ever had watery diarrhea after a course of amoxicillin or azithromycin, you’re not alone. Studies show S. boulardii cuts the risk of antibiotic-associated diarrhea by nearly half. It’s also been shown to help with traveler’s diarrhea, C. diff infections, and even chronic gut issues like IBS. But it’s not magic—it works best when taken at the right time, in the right dose, and without interference from other meds. For example, antifungal drugs like fluconazole can kill it off, making it useless. And if you’re immunocompromised, you should talk to your doctor first—yeast in the gut isn’t always safe for everyone.

People often confuse it with other probiotics, but S. boulardii has unique traits. It doesn’t need refrigeration, it resists antibiotics, and it helps your body produce enzymes that break down toxins. It’s found in capsules, powders, and sometimes even in combination products with other gut-supporting ingredients. What you won’t find in most supplements is clear labeling about strain specificity—so look for "Saccharomyces boulardii CNCM I-745" or "Lyo-Ferm" on the label. Those are the strains backed by real clinical data.

Below, you’ll find real-world advice from people who’ve used it, doctors who’ve prescribed it, and studies that show exactly how it works. Whether you’re trying to recover from an infection, manage recurring diarrhea, or just understand why your gut feels off after meds, these posts give you the facts—not the fluff.