What is SIBO Testing?

Dr.Neda Moeini, ND 05 Jul 2024

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SIBO breath testing is a non-invasive testing alternative to small intestinal culture to diagnose SIBO (Small Intestine Bacterial Overgrowth) and IMO (Intestinal Methanogen Overgrowth). A SIBO breath test is performed the morning after a patient follows a restrictive preparatory diet and overnight fast. The test begins with the patient collecting a baseline breath sample and drinking a water mixture containing either glucose or lactulose..

Bacteria and archaea in the gastrointestinal (GI) tract ferment carbohydrates produce hydrogen, methane, and hydrogen sulfide gases. These gases diffuse into the bloodstream and are exhaled through the lungs. Elevations of gas levels during the SIBO breath test are diagnostic for the overgrowth of bacteria and/or methanogens in the GI tract. Test is positive if at least one of the following criteria is met:

Hydrogen-SIBO: hydrogen levels rise at least 20 ppm from baseline within the first 90 minutes of the test
IMO: methane level is at least 10 ppm at any time point during the test
Hydrogen sulfide-SIBO: hydrogen sulfide level is at least 3 ppm at any time point during the test

Glucose and lactulose breath tests both offer their own benefits. Glucose is absorbed within the first three feet of the small intestine; the advantage of a glucose breath test is that it limits the number of false positive test results, and it can accurately diagnose overgrowth within the proximal small intestine. Humans cannot digest or absorb lactulose; the advantage of a lactulose breath test is that it can diagnose overgrowth in the distal portions of the small intestine, which is thought to be more common.

Which Patients is SIBO Testing Best Used For?

SIBO has been correlated with many digestive and non-digestive symptoms and medical conditions. Over two-thirds of patients with diagnosed SIBO report digestive symptoms, including bloating, abdominal pain, belching, flatulence, indigestion, constipation, and diarrhea. Symptoms can vary in frequency, duration, and severity. Irritable bowel syndrome is a functional bowel disorder diagnosed when abdominal pain and irregular bowel movements are present for at least six months.

SIBO testing can benefit other patients, too, as SIBO has been associated with a variety of other conditions, including inflammatory bowel disease, Rosacea, Restless legs syndrome, Pancreatitis, Hypothyroidism, Parkinson's disease Diabetes, and coronary artery disease.