What is a Lactose Intolerance Test?

Lactose intolerance is a condition that affects people who lack an enzyme called lactase. This enzyme breaks down lactose, a type of sugar present in dairy products. A lactose-intolerant person who eats dairy products will suffer from symptoms such as abdominal pain, bloating, gas and diarrhea as a result of his or her inability to break down lactose. This condition is diagnosed using a lactose intolerance test that measures one or more effects of lactose on the person being tested. There are several types of lactose intolerance tests that might be used to diagnose lactose intolerance.

The hydrogen breath lactose intolerance test measures the amount of hydrogen present in a person’s breath after they have ingested lactose. In this test, the patient must drink a lactose-containing liquid. At several time-points after drinking the liquid, the patient’s breath is tested for hydrogen. This is carried out by having the patient breathe into an analysis tool that is capable of detecting the gas. Undigested lactose generates hydrogen, so people who are lactose intolerant will continue to have hydrogen in their breath for some time after drinking the liquid.

The second type of lactose intolerance test is a blood test that measures blood glucose levels after the ingestion of lactose. As with the hydrogen breath test, this method has the patient drink a lactose-containing liquid. The patient will have a blood sample taken before drinking the liquid, and more samples are taken at several time-points afterward. Each sample is tested for the presence of glucose, because this sugar is produced when lactose is broken down by the lactase enzyme.

Another type of lactose intolerance test that might be used is the stool acidity test. This test is most often used to test infants and young children. In the stool acidity test, a sample of the child’s stool is analyzed for the presence of fatty acids such as lactic acid. These acids are present in abnormally high amounts in a child who is not able to digest lactose.

Lactose intolerance is not a curable condition, but the symptoms can be managed by making dietary changes. The type of changes needed varies on an individual basis, because people differ in the amount of lactose they can tolerate. For some, a small glass of milk might be enough to produce severe symptoms, and others might be able to drink the same amount of milk without any problems.