How is Small Intestinal Bacterial Overgrowth (SIBO) diagnosed?

Small Intestinal Bacterial Overgrowth (SIBO) is diagnosed primarily through a carbohydrate breath test. This method is effective because it measures the concentration of hydrogen and/or methane in the breath after the ingestion of a carbohydrate substrate, usually lactulose or glucose. If SIBO is present, the bacteria in the small intestine will ferment the carbohydrate, producing hydrogen or methane, which will then be absorbed into the bloodstream and eventually exhaled. Elevated levels of these gases within a specific timeframe indicate the presence of SIBO.

The carbohydrate breath test is favored due to its non-invasive nature and ability to provide results quickly. Understanding the underlying mechanism of SIBO diagnosis through breath testing highlights the importance of bacterial fermentation in carbohydrate metabolism, which is central to confirming the presence of an overgrowth.

Other diagnostic methods, such as blood tests, stool analyses, or endoscopy, are not standard for SIBO and do not specifically indicate bacterial overgrowth in the small intestine. Blood tests may reveal signs of malabsorption or nutritional deficiencies, stool analyses can assess overall gut health but not specifically pinpoint SIBO, and while endoscopy allows for direct visualization of the intestine, it is generally not employed purely for the diagnosis of SIBO. Therefore