SIBO Symptom Checker

Small Intestinal Bacterial Overgrowth (SIBO) occurs when excessive bacteria colonize the small intestine, fermenting food before your body can absorb the nutrients. This fermentation produces hydrogen, methane, or hydrogen sulfide gas — causing the bloating, pain, and altered bowel habits that characterize SIBO.

The hallmark symptom of SIBO is bloating that begins within 30 to 90 minutes of eating, often accompanied by visible abdominal distension. Unlike occasional bloating from overeating, SIBO bloating occurs predictably after meals and worsens with high-FODMAP foods like garlic, onions, beans, and wheat. Many patients describe it as feeling "six months pregnant" after a normal-sized meal.

SIBO symptoms differ by type. Hydrogen-dominant SIBO typically causes diarrhea and urgent bowel movements. Methane-dominant SIBO (also called Intestinal Methanogen Overgrowth or IMO) causes constipation, as methane gas slows intestinal transit. Hydrogen sulfide SIBO may produce rotten-egg-smelling gas and diarrhea. Beyond digestive symptoms, SIBO commonly causes fatigue, brain fog, and nutritional deficiencies — especially B12 and iron.

If this assessment suggests your symptoms are consistent with SIBO, the next step is a breath test. The gold standard is a lactulose breath test that measures gas levels over 2 to 3 hours. This can be done in a doctor's office or at home with kits from providers like Trio-Smart or Aerodiagnostics. A positive result — a rise of 20+ ppm hydrogen or 10+ ppm methane above baseline within 90 minutes — confirms the diagnosis.