Normal Values:

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.

What abnormal results mean:

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.