Lactose Tolerance Tests Test
Lactose tolerance tests check if your body can break down lactose, a sugar in dairy products. If you can't digest lactose, you may have lactose intolerance, which causes gas, bloating, and diarrhea after eating dairy.
What this test measures
Lactose tolerance tests measure your body's ability to break down lactose. Normally, an enzyme called lactase breaks down lactose into simpler sugars that are absorbed for energy. If your body doesn't make enough lactase, you won't properly digest foods with lactose.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
For the hydrogen breath test, an increased level of hydrogen and worsening symptoms after drinking lactose probably means you have lactose intolerance.
Lower-than-normal results
For the glucose blood test, if your glucose levels did not increase after drinking lactose, this probably means you have lactose intolerance.
Frequently asked questions
What is lactose intolerance?
Lactose intolerance is when you get symptoms like gas, bloating, and diarrhea after eating or drinking dairy products because your body can't digest all the lactose.
How do lactose tolerance tests work?
There are two types: a hydrogen breath test measures hydrogen in your breath before and after drinking lactose, and a glucose blood test measures blood glucose before and after drinking lactose.
What does a high hydrogen level mean?
An increased level of hydrogen and worsening symptoms after drinking lactose probably means you have lactose intolerance.
What does no increase in blood glucose mean?
If your glucose levels did not increase after drinking lactose, this probably means you have lactose intolerance.
Can I still have lactose intolerance if my test is negative?
Yes, sometimes you can have a negative result and still have lactose intolerance. You may need more tests to find the cause of your symptoms.
Related lab tests
Sources
- MedlinePlus: Lactose Tolerance Tests — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.