Florastor Daily Probiotic

Florastor is the #1 prescribed probiotic worldwide, and for one reason that no bacterial probiotic can match: it’s a yeast. Saccharomyces boulardii CNCM I-745 is naturally immune to every antibiotic, which means you can take Florastor alongside your antibiotic prescription without the probiotic being destroyed. For adults over 50 — who are prescribed antibiotics more frequently than younger populations — this is a critical advantage backed by over 100 clinical studies and 65 years of global use.

What Is Florastor?

Florastor is made by Biocodex, a French pharmaceutical company that has been producing this probiotic since 1953. The active ingredient — Saccharomyces boulardii CNCM I-745 — was first discovered in 1923 by French scientist Henri Boulard, who observed people in Southeast Asia chewing the skin of lychee and mangosteen fruits during cholera outbreaks.

Unlike Lactobacillus or Bifidobacterium-based probiotics, Florastor is a beneficial yeast. This isn’t just a marketing distinction — it fundamentally changes how the probiotic works in your gut. Yeast operates through different mechanisms than bacteria: it binds directly to harmful pathogens, strengthens the intestinal lining, and supports your existing bacterial flora without competing with it.

Florastor is prescribed by doctors in over 100 countries. In many European and South American countries, it’s a standard part of antibiotic therapy — prescribed alongside the antibiotic, not just suggested.

What’s Inside

Each capsule contains:

• 250mg of Saccharomyces boulardii CNCM I-745 (the lyophilized, or freeze-dried, form equals approximately 5 billion cells)

The recommended dose is two capsules daily (500mg total), which aligns with the dosing used in most clinical trials. Other ingredients include lactose (trace amounts as a growth medium), magnesium stearate, gelatin (capsule), and titanium dioxide.

The CNCM I-745 strain designation is important — not all Saccharomyces boulardii products use the same strain, and the clinical evidence specifically supports this one. Florastor is the only S. boulardii product in the U.S. that uses the CNCM I-745 strain with full clinical documentation.

What the Research Says

The evidence base for Saccharomyces boulardii is extensive and well-established.

A 2010 meta-analysis published in the World Journal of Gastroenterology analyzed 25 randomized controlled trials and found that S. boulardii reduced antibiotic-associated diarrhea by 52%. This remains one of the most robust findings in all of probiotic research.

For Clostridioides difficile infection — a serious concern for older adults, especially after hospital stays — a 2017 Cochrane review found moderate-quality evidence that S. boulardii reduces the risk of C. difficile-associated diarrhea when taken alongside antibiotics.

Traveler’s diarrhea is another well-studied application. A meta-analysis in the American Journal of Gastroenterology found that prophylactic use of S. boulardii significantly reduced the incidence of traveler’s diarrhea.

Research published in Alimentary Pharmacology & Therapeutics has also shown benefits for chronic digestive conditions, with S. boulardii demonstrating anti-inflammatory effects and improved intestinal barrier function in multiple studies.

Who Is This Best For?

Florastor fills a specific niche that no bacterial probiotic can:

• Anyone taking antibiotics — this is Florastor’s primary use case, and the evidence is strongest here. The yeast cannot be killed by antibiotics.
• Adults over 50 with recurrent C. difficile concerns — especially those who’ve been hospitalized or taken multiple antibiotic courses
• Travelers — S. boulardii has specific evidence for preventing traveler’s diarrhea, and the shelf-stable capsules travel easily
• People already taking a bacterial probiotic — Florastor works through different mechanisms and complements (rather than competes with) bacterial strains like Lactobacillus and Bifidobacterium

Florastor is not a complete microbiome solution on its own. It does not contain the Lactobacillus or Bifidobacterium species that support general gut diversity. For comprehensive daily gut health, many practitioners recommend combining Florastor with a bacterial probiotic.

How to Take It

Take one capsule twice daily (total 500mg/day). You can take it with or without food — and critically, you can take it at the exact same time as your antibiotic. No spacing required.

The capsules can be opened and mixed into a cool or room-temperature beverage or soft food if swallowing capsules is difficult. Do not mix with hot liquids — heat kills the yeast.

For antibiotic support, begin Florastor on the same day you start your antibiotic and continue for at least two weeks after completing the antibiotic course. For travel, start 5-7 days before departure and continue throughout your trip.

Store at room temperature. Florastor is shelf-stable but performs best when kept below 77°F (25°C).

The Bottom Line

Florastor occupies a unique position in the probiotic world. As the only widely available yeast-based probiotic with decades of clinical evidence, it solves a problem that bacterial probiotics fundamentally cannot: surviving alongside antibiotics. For adults over 50 who take antibiotics periodically, travel, or want an additional layer of gut protection on top of their bacterial probiotic, Florastor is backed by the kind of evidence that makes pharmacists recommend it with confidence.

Always consult your doctor before starting any probiotic, especially if you are immunocompromised, have a central venous catheter, or are being treated for a serious infection. Individuals with yeast allergies should avoid Florastor.