Lactose Tolerance Hydrogen (Breath)
Does this test have other names?
Hydrogen breath test, HBT, lactose breath test
What is this test?
This test measures the amount of hydrogen gas in your breath at regular intervals.
It will show how well your body breaks down lactose, the sugar found in dairy products,
and fructose, the sugar in fruit. This test also shows whether you have a high amount
of bacteria in your small intestine.
Normally, the lactose you eat is broken down in your small intestine. If it can't
be broken down there, it goes to your colon, or large intestine. In the colon, the
lactose can ferment, causing excess hydrogen. This extra hydrogen is absorbed into
your blood and travels to the lungs, where you release it in your breath.
Why do I need this test?
You might have this test if you have symptoms of lactose intolerance. Symptoms include:
Lactose intolerance is more common in people of certain ethnic backgrounds. These
include African, Hispanic/Latino, American Indian, and Asian.
You also might have this test if you have an intestinal problem like inflammatory
bowel disease or a malabsorption syndrome like short gut syndrome. Infants who are
not gaining enough weight may also have this test.
What other tests might I have along with this test?
Your healthcare provider might also order a glucose tolerance test, which is used
mainly to diagnose diabetes. A glucose tolerance test can help tell whether your symptoms
are caused by lactose intolerance or diarrhea from malabsorption.
If this test is for your child, he or she may have stool tested for acidity. A child
may have glucose in his or her stool because of undigested lactose.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Normal test results compare your exhaled breath before and after you drink liquid
containing sugar. The amount of hydrogen gas in your breath should increase by no
more than 20 parts per million.
If your breath test shows you are exhaling large amounts of hydrogen, it may mean
you aren't fully digesting and absorbing lactose.
How is this test done?
This test requires several breath samples over a period of time. You will first breathe
into a bag. Then you will drink a beverage that contains lactose, fructose, or other
sugars. You must drink it all. Every 15 minutes for the next 2 to 4 hours, you will
be asked to breathe into a bag. Each time, a technician will empty the bag with a
Does this test pose any risks?
If you are lactose intolerant, drinking the sugar may cause bloating, cramps, diarrhea,
What might affect my test results?
Your results could be affected if you:
Exercise strenuously before or during testing
Take antibiotics within a month before testing
Eat or drink while testing
Smoke before or during testing
Chew gum or breath mints during testing
How do I get ready for this test?
Stop taking antibiotics at least 4 weeks before your test.
The day before your test, do not eat high-fiber foods such as beans or whole-grain
cereals. Don't drink carbonated beverages.
Fast for 12 hours before testing. That means you should have nothing to eat or drink.
Don't smoke the day before testing.
Don't exercise strenuously the day before testing.
Brush your teeth 2 hours before your test begins, or as directed by your healthcare
Your healthcare provider may give you other dietary instructions. Be sure your provider
knows about all medicines, herbs, vitamins, and supplements you are taking. This includes
medicines that don't need a prescription and any illicit drugs you may use.