Health & Well-Being A-Z

Bacillus subtilis


Bacillus subtilis (B. subtilis) is a type of probiotic ("good" bacteria) found naturally in the human gut. It's also found in fermented foods.

"Good" bacteria such as B. subtilis might help the body break down food, absorb nutrients, and fight off "bad" organisms that might cause diseases. These bacteria are sometimes added to fermented foods like yogurt and also found in dietary supplements.

People use B. subtilis for diarrhea from antibiotics. It is also used for athletic performance, eczema, constipation, indigestion, gas, irritable bowel syndrome (IBS), and many other conditions, but there is no good scientific evidence to support most of these uses.

Don't confuse B. subtilis with Bacillus coagulans, other probiotics, nattokinase, or with fermented food products such as fermented milk, kefir, or yogurt. These are not the same. Also note that three previously recognized Bacillus subtilis subspecies have recently been reclassified. Some products marketed as B. subtilis might actually contain these newly classified Bacillus species, including Bacillus inaqosorum, Bacillus spizizenii, and Bacillus stercoris.

Is It Effective?

Effectiveness header

NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

Possibly effective
  • Diarrhea in people taking antibiotics (antibiotic-associated diarrhea). Taking B. subtilis by mouth seems to help prevent diarrhea from antibiotics.

There is interest in using B. subtilis for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.

Is it Safe?


When taken by mouth: Some B. subtilis strains are commonly consumed in foods. As medicine, B. subtilis is possibly safe for most people. B. subtilis strains BS50, B2335, CU1, MB40, MY02, and R0179 have been used safely in doses of 2-10 billion colony-forming units (CFUs) daily for 2-8 weeks. It seems to be well-tolerated.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if B. subtilis is safe to use when pregnant or breast-feeding. Stay on the safe side and stick to food amounts.

Children: There isn't enough reliable information to know if Bacillus subtilis is safe for children, including very small premature infants.

Weakened immune system: Probiotics have caused blood infections in a small number of people with weakened immune systems. If you have a weakened immune system, talk with your healthcare provider before taking probiotics, including B. subtilis.

Drug interactions

Antibiotic drugs

Interaction Rating=Moderate Be cautious with this combination.

B. subtilis is a type of friendly bacteria. Antibiotics are used to reduce harmful bacteria in the body. Taking antibiotics along with B. subtilis can reduce the effects of B. subtilis. To avoid this interaction, take B. subtilis products at least 2 hours before or after antibiotics.

Herb interactions

There are no known interactions with herbs and supplements.

Food interactions

There are no known interactions with foods.


In adults, B. subtilis has most often been taken by mouth alone or together with other probiotics in doses of 2-5 billion colony-forming units (CFUs) daily for up to 8 weeks. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.

Other names

B. subtilis, B. subtilis natto, Bacillus inaqosorum, Bacillus spizizenii, Bacillus stercoris, Bacillus subtilis subsp. inaqosorum, Bacillus subtilis subsp. spizizenii, Bacillus subtilis subsp. stercoris, Bacillus subtilis subsp. subtilis, Bacillus subtilis subsp. subtilis var. natto, DE111.


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