Lactose Tolerance Test (cont.)

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How is the lactose tolerance test done?

The lactose tolerance test requires an individual to drink a liquid that contains lactose. In the small intestine among lactose tolerant individuals, the ingested lactose is split into galactose and glucose which then are absorbed from the intestine and go into the blood. Several blood samples are taken over a two hour period following the ingestion of the lactose to measure the blood glucose level. If lactose tolerance is normal, the glucose level in the blood rises due to the absorption of glucose from the intestine. If there is lactose intolerance, the glucose level does not rise.

What other tests can detect lactose intolerance?

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Many clinicians simply make this diagnosis based on improvement of symptoms when lactose is withheld from the patient's diet and affravation when it is re-introduced. Other tests used to detect lactose intolerance include the lactose hydrogen breath test and stool acidity test, the latter is primarily used in infants and very young children. There also is a genetic test which can determine whether an individual has or does not have the intestinal enzyme that is required for the digestion and absorption of lactose.

Medically reviewed by Rambod Rouhbakhsh, MD, MBA, FAAFP; American Board of Family Medicine


"Lactose intolerance"

Medically Reviewed by a Doctor on 3/4/2014

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Lactose Intolerance Test - Indications Question: Did your doctor administer a lactose intolerance test, or diagnose you based on diet?