Diagnostic Tests for Lactose Intolerance


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Diagnostic Test list for Lactose Intolerance: The list of diagnostic tests mentioned in various sources as used in the diagnosis of Lactose Intolerance includes:

Tests and diagnosis discussion for Lactose Intolerance: The most common tests used to measure the absorption of lactose in the digestive system are the lactose tolerance test, the hydrogen breath test, and the stool acidity test. These tests are performed on an outpatient basis at a hospital, clinic, or doctor's office.

The lactose tolerance test begins with the individual fasting (not eating) before the test and then drinking a liquid that contains lactose. Several blood samples are taken over a 2-hour period to measure the person's blood glucose (blood sugar) level, which indicates how well the body is able to digest lactose.

Normally, when lactose reaches the digestive system, the lactase enzyme breaks down lactase into glucose and galactose. The liver then changes the galactose into glucose, which enters the bloodstream and raises the person's blood glucose level. If lactose is incompletely broken down the blood glucose level does not rise, and a diagnosis of lactose intolerance is confirmed.

The hydrogen breath test measures the amount of hydrogen in the breath. Normally, very little hydrogen is detectable in the breath. However, undigested lactose in the colon is fermented by bacteria, and various gases, including hydrogen, are produced. The hydrogen is absorbed from the intestines, carried through the bloodstream to the lungs, and exhaled. In the test, the patient drinks a lactose-loaded beverage, and the breath is analyzed at regular intervals. Raised levels of hydrogen in the breath indicate improper digestion of lactose. Certain foods, medications, and cigarettes can affect the test's accuracy and should be avoided before taking the test. This test is available for children and adults.

The lactose tolerance and hydrogen breath tests are not given to infants and very young children who are suspected of having lactose intolerance. A large lactose load may be dangerous for very young individuals because they are more prone to dehydration that can result from diarrhea caused by the lactose. If a baby or young child is experiencing symptoms of lactose intolerance, many pediatricians simply recommend changing from cow's milk to soy formula and waiting for symptoms to abate.

If necessary, a stool acidity test, which measures the amount of acid in the stool, may be given to infants and young children. Undigested lactose fermented by bacteria in the colon creates lactic acid and other short-chain fatty acids that can be detected in a stool sample. In addition, glucose may be present in the sample as a result of unabsorbed lactose in the colon. 1

doctor will use one of these tests:

Blood and breath tests
You will drink a sweet drink with lactose in it. Then, your doctor will test your breath or blood for signs that you did or did not digest the lactose. 2

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 lactase. 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 stomach. 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. 3

Footnotes:
1. excerpt from Lactose Intolerance: NIDDK
2. excerpt from Why Does Milk Bother Me: NIDDK
3. excerpt from Lactose Intolerance: NWHIC

Last revision: May 30, 2003

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