Definition: There are three methods for determining if a person suffers from lactose intolerance. The first is a non-invasive measurement of the amount of hydrogen in the breath. The second option requires a series of blood samples taken over brief intervals. These first two tests require fasting prior to the test and the drinking of a solution that contains lactose. The third option is a test for a genetic marker for lactose malabsorption, which is a blood test that requires no fasting or dietary restrictions. The downside of this test is the expense, which might preclude it from being covered by insurance companies.

