thy digestive system, the sugars and carbohydrates that you eat are predigested before they reach the bacteria in your colon. If they haven’t been fully digested by then, the anaerobic bacteria will digest them, converting them into gas. Advertisement The gas in your colon is absorbed into your blood and carried into your lungs, where it’s expelled through your breath. That’s how your breath can show what’s going on in your gut. The hydrogen breath test measures hydrogen levels in your breath after consuming a particular sugar. The amount of hydrogen, and how fast it’s produced, gives your healthcare provider information about how your digestion is working. Do breath tests measure other gases? Methane: Because everyone’s assortment of gut bacteria is a little different, some people have more methane in their breath than hydrogen. For this reason, most clinics today measure for both gasses at the same time. Both are measured in the same way. However, the methane test is more recent and may not be as accurate as the hydrogen breath test. Carbon dioxide: A different type of breath test measures carbon dioxide (CO2) levels in your breath. The H. pylori breath test is one. This test is separate from the hydrogen breath test because of what you ingest during the test. While the hydrogen breath test measures your digestion of sugars or carbohydrates, the carbon breath tests require you to consume a solution of carbon molecules. The two tests are used separately to diagnose different gastrointestinal diseases . What are the different types of hydrogen breath tests? When you take a hydrogen breath test, you’ll give a breath sample before and several after consuming a particular test sugar — usually lactose, fructose, sucrose, sorbitol, glucose or lactulose. The choice of sugar depends on what kind of condition your healthcare provider is checking for. Lactose, fructose, sucrose and sorbitol tests check for intolerance to those particular sugars. These are all sugars that, fo