Diagnosis of Lactose Intolerance

If you think that you are lactose intolerant, it is important to have a doctor diagnose you because your symptoms could be a sign of a different, or more serious, illness. There are three tests used to determine if a person has lactose intolerance: the lactose tolerance test; the hydrogen breath test; and the stool acidity test. All of these tests are performed on an outpatient basis.

The lactose tolerance test is a blood test that measures the amount of glucose in the blood before and after the patient drinks a large amount of liquid containing lactose. The patient is required to fast before the test. The hydrogen breath test measures the amount of hydrogen in the breath. The patient has to fast overnight and again at regular intervals after taking a dose of lactose. If the lactose is not digested, it produces hydrogen and other gases in the large intestine. These gases travel through the body to the mouth and can be detected in the breath. The stool acidity test detects acids created by undigested lactose.