What it measures
A test of whether the body digests lactose, the sugar in milk. Blood glucose is measured after fasting and then several times after a lactose drink. If lactose is digested, glucose rises.
Why people test it
- Used to look into bloating, wind or diarrhoea after milk or dairy foods.
- A blood-based alternative to the hydrogen breath test for lactose intolerance.
Typical range
Labs read the result as the rise in glucose after the drink. Ranges and cut-offs vary by lab, method, age and sex, and your report shows the lab's own range and reading.
Finger-prick or vein?
Several vein samples are taken during the test, so it is done at a clinic or by a visiting nurse rather than with a home kit.
The test starts after an overnight fast, and samples are taken over about two hours.