Hydrogen breath test for lactose tolerance
The breath test is considered normal if the increase in hydrogen is less than 12 parts per million over your fasting (pre-test) level.
The blood test is considered normal if your glucose level rises more than 30 mg/dL within 2 hours of drinking the lactose solution. A rise of 20-30 mg/dL is inconclusive.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
Abnormal results may be a sign of lactose intolerance.
A breath test result that shows a rise in hydrogen content of 12 parts per million (ppm) over your pre-test level is considered positive, and means you may have trouble breaking down lactose.
The blood test is considered abnormal if your glucose level rises less than 20 mg/dL within 2 hours of drinking the lactose solution.
An abnormal test should be followed by a glucose tolerance test to rule out a problem with the body's ability to absorb glucose.
Hogenauer C, Hammer HF. Maldigestion and malabsorption. In: Feldman M, Friedman LS, Sleisenger MH, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 101.
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