Medical Health Encyclopedia

Lactose tolerance test

For an infant or young child:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test:

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Fast for 8 hours and avoid strenuous exercise for 8 hours before the test.

How the test will feel:

The breath sample is collected in either a special bag or syringe, and should not be associated with any pain or discomfort.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

This test is used to diagnose lactase deficiency.

Lactose is a disaccharide (a type of sugar) in dairy products. During digestion, lactose is broken down into glucose and galactose, two simple sugars, by the intestinal enzyme lactase. Lactose-intolerant patients have a deficient or absent lactase enzyme. Bacteria metabolize the undigested lactose, producing gases such as hydrogen and other acid products.

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