Lactulose is a carbohydrate that is not absorbed by humans. Lactulose is well known to measure oro-cecal transit time. The mean oro-cecal transit time in normal healthy individuals is 70 to 90 minutes. By 90 minutes, at least 50% of individuals would have delivered the lactulose dose to the colon. Approximately 90 to 95% of individuals have colonic bacteria that can metabolize lactulose to hydrogen or methane gas. Thus, any SIBO breath test that collects longer than 60 minutes may be measuring colonic activity. Diagnostic criteria of 20 ppm hydrogen and/or methane changes within 90 or 120 minutes will have higher positive rates of SIBO but this will reflect colonic activity not jejunal metabolism. A one-hour SIBO breath test avoids false positive results by collecting breath up to 60 minutes.