Evaluation of Lactose Breath Test Results

When lactose is not fully absorbed, it passes from the small intestine to the large intestine or colon. Our colon has bacteria that will degrade lactose to simple gases like hydrogen or methane. It is thought that these gases are responsible for the gastric distress that some people feel after consuming lactose containing foods. In the lactose breath test, we administer a 25 gram amount of lactose and collect breath samples for 3 hours.

Each breath sample is analyzed for hydrogen, methane and carbon dioxide levels. The hydrogen and methane levels are standardized to the amount of breath carbon dioxide in the sample we receive. We determine the change in hydrogen and methane from the initial breath collection. A change of at least 20 parts per million is considered lactose intolerance. Shown below are examples of normal and lactose intolerance test results:


Lactose Intolerance