The SIBO (Small Intestinal Bacterial Overgrowth) Breath Test is a non-invasive test that measures the levels of hydrogen and methane in your breath after ingesting lactitol. These gases are produced by bacteria when they ferment carbohydrates in the small intestine, where they should not normally be present explaining persistent digestive symptoms such as bloating, abdominal pain, diarrhoea or constipation. Bacterial overgrowth is detected using the breath test, the reference functional method for identifying this condition.