Hydrogen breath test

A hydrogen breath test (HBT) or hydrogen-methane breath test is a breath test used as a diagnostic tool for small intestine bacterial overgrowth (SIBO), and carbohydrate malabsorption, such as lactose, fructose, and sorbitol malabsorption.

The test is a simple, non-invasive procedure, and is performed after a short period of fasting (typically 8–12 hours). Hydrogen breath tests are based on the fact that there is no source for hydrogen gas in humans other than bacterial metabolism of carbohydrates. The test is normally known as a hydrogen breath test, but often includes testing for methane. Many studies have shown that some people (approximately 35% or more) do not produce hydrogen but actually produce methane, and sometimes a combination of the two gases is found. Other people, who are known as "non-responders", don't produce any gas; it has not yet been determined whether they may actually produce another gas. In addition to hydrogen and methane, some facilities also utilize carbon dioxide (CO₂) in the patient's breath to determine if the breath samples that are being analyzed are contaminated (either with room air or bronchial dead space air).

Physicians have expressed concern at the improper use and widespread overdiagnoses related to interpretation of these tests.