Small intestinal bacterial overgrowth is a medical condition in which a person has an unusually large population of bacteria in their small intestine. This can happen when bacteria from one part of the digestive tract travels to the small intestine.

It is more likely to affect females, older adults, and people with digestive issues, such as irritable bowel syndrome (IBS). Some symptoms may include bloating, stomach pain, diarrhea and nausea.

If a doctor suspects SIBO they will likely recommend a breath test in which a measurement is taken of the hydrogen and methane is a person’s breath. Bacteria produce hydrogen and methane when they break down carbohydrates in the gut, meaning gut bacteria feed on carbohydrates. Those molecules then travel through the blood and leave the body in the form of your breath. 

SIBO can be treated with antibiotics and changes in diet. In general, the SIBO diet limits carbohydrate intake to prevent bacteria from growing. People who have SIBO can work with a doctor or nutritionist to tailor their diet to manage their symptoms.