Lactose Malabsorption Test in Idaho

What this test measures

Lactose is a sugar in milk and dairy products. It is digested by lactase, an enzyme in the small intestine. When lactase activity is low, undigested lactose passes into the colon, where bacteria ferment it and cause gas, bloating, cramps, and diarrhea.

During the test, a person drinks a lactose solution after a fasting period. Blood samples are taken at intervals to measure glucose, and the person reports any symptoms. A rise in glucose suggests lactose was digested, while a flat curve suggests malabsorption. Some providers also measure hydrogen in breath instead.

Providers order lactose testing when digestive symptoms follow milk, ice cream, or other dairy products, and when other causes have been considered. Lactose intolerance differs from milk allergy, which involves the immune system. A qualified healthcare provider should interpret the test and advise on diet changes.