Functional abnormality of the gastrointestinal tract Positive hydrogen breath test 2024-02-04T06:29:33Z Positive glucose or lactulose hydrogen breath test Positive glucose hydrogen breath test Abnormally elevated quantiy of hydrogen measured by a hydrogen breath test (HBT). HBTs administer substrates such as glucose, lactulose, lactose and fructose and subsequently measure hydrogen exhaled in the breath using a gas chromatograph. Bacteria, especially anaerobic, colonizing the large bowel in health and small bowel in diseased conditions produce hydrogen by fermentation of unabsorbed carbohydrates. Though small amount of hydrogen is produced from limited amounts of unabsorbed carbohydrate reaching the colon, large amounts of hydrogen may be produced if there is malaborption of carbohydrate in the small intestine allowing larger amount to reach the colon or if there is excess of bacteria in the small bowel. The hydrogen produced by the bacteria is absorbed through the wall of the small or large intestine or both. The hydrogen-containing blood travels to the lungs where the hydrogen is released and exhaled in the breath where it can be measured. Positive lactulose hydrogen breath test