What is the hydrogen breath test?

The hydrogen breath test is used to identify one of two conditions: lactose intolerance or an abnormal growth of bacteria in the intestine.

What is lactose intolerance?

Lactose intolerance is the inability to digest lactose, the sugar found in milk. Lactose intolerance occurs because the person’s body may not have any lactase, an enzyme that is normally produced by the small intestine. Lactase is needed to digest lactose. Symptoms of lactose intolerance include cramping, bloating, gas, or diarrhea when dairy products are eaten and drunk.

What is bacterial overgrowth in the intestine?

Normally, small amounts of bacteria are found in the intestine. If there is a large increase in the amount of bacteria, food and nutrients are not being absorbed properly.

Bacterial overgrowth can result from a slow transit (passage) of food through the bowels, or from certain medications. Symptoms of bacterial overgrowth may include abdominal pain, bloating, gas, and diarrhea.

Last reviewed by a Cleveland Clinic medical professional on 05/16/2016.

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