SIBO is characterised by an increase in the number, or a change in, the type of bacteria found in the small intestine.

The detection of hydrogen and methane in the breath after ingesting a substrate (Glucose) can help determine if SIBO is the cause of gastrointestinal symptoms such as diarrhoea, constipation, bloating, cramping, nausea, reflux, flatulence and belching. Such symptoms, often non-specific and indistinguishable from those seen in irritable bowel syndrome (IBS) and other functional digestive disorders, can be the result of bacterial fermentation of short chain carbohydrates in the small intestine.

Risk factors for SIBO include achlorhydria, use of proton pump inhibitors (PPIs), pancreatitis, diabetic neuropathy, migrating motor complex (MMC) impairment, gastroenteritis, motility disorders, Crohn's Disease, IBS and Coeliac Disease. This simple test is non-invasive, performed at home and requires a 1-2-day preparatory diet and a 12-hours fasting period