A breath test is a noninvasive method of measuring the levels of certain gases in your breath to determine the presence of various digestive disorders.

Some people have difficulty digesting certain sugars such as fructose (fructose intolerance) and lactose (lactose intolerance). These undigested sugars move to the colon, where they get digested by bacteria and release hydrogen. Small intestine bacterial overgrowth syndrome (SIBO) is another digestive condition characterized by the uncontrolled growth of bacteria in the small intestine, which digest food and release gas. Infection with the bacteria Helicobacter pylori erodes the lining of the stomach, leading to ulcers, gastritis and gastric cancer, and can be detected by carbon dioxide released into the blood and transported to your lungs. These digestive conditions are characterized by bloating, gas, cramping or diarrhea.

A breath test measures the levels of gases that these bacteria produce, which can be detected in your breath. It is usually performed after fasting. You are instructed to breathe into a breath-analyzing machine before and at regular intervals after consuming a specific solution depending on what is being tested. The machine measures the level of hydrogen and carbon dioxide gas produced by the bacteria and helps determine the diagnosis of the digestive disorder.