Hydrogen Breath Test

What is a hydrogen breath test?

A hydrogen breath test (HBT, lactose breath test or fructose breath test) measures a patient’s breath to see if they are digesting sugar adequately in the intestine. The amount of hydrogen gas in the breath is measured at regular intervals after ingesting a measured amount of lactose or fructose. It will show how well a patient’s body breaks down lactose, the sugar found in dairy products, and fructose, the sugar in fruit. This test can also show the amount of bacteria in the small intestine when lactulose is the sugar tested.

Normally, lactose is broken down in the small intestine. If it can’t be broken down there, it goes to the colon (large intestine). In the colon, the lactose can ferment, causing excess hydrogen.  This extra hydrogen is absorbed into the blood and travels to the lungs, where it is release through breathing.

Why would a child need a hydrogen breath test?

A child might have this test if they have symptoms of lactose or fructose intolerance. Symptoms include:

  • Gas
  • Stomach cramps
  • Bloating
  • Diarrhea, especially after they eat or drink milk and other dairy products such as ice cream and cheese.

Learn more about lactose intolerance.

Children may also have this test if they have an intestinal problem like inflammatory bowel disease or a malabsorption syndrome like short bowel syndrome.

What is a glucose tolerance test?

Your child’s doctor might order a glucose tolerance test, which is used mainly to diagnose diabetes. A glucose tolerance test should not be confused with a breath hydrogen test.

What do my child’s hydrogen breath test results mean?

Many things may affect your child’s lab test results. Even if your child’s test results are different from the normal value, there may not be a significant problem. To learn what the results mean for your child, it is important to speak with their doctor.

Normal test results compare your child’s exhaled breath before and after they drink liquid containing sugar. The amount of hydrogen gas in your child’s breath should increase by no more than 50 parts per million.

If the breath test shows the child is exhaling large amounts of hydrogen, it may mean the child isn’t fully digesting and absorbing the sugar.

How is this test done?

This test requires several breath samples over a period of time. The child first breathes into a bag. Then, they drink a beverage that contains lactose, fructose or other sugars. They must drink it all. Every 15 minutes afterward, for the next two to four hours, the child will be asked to breathe into a bag. Each time, a technician will empty the bag with a syringe. There is no blood testing required.

Does this test pose any risks?

If the child is lactose or fructose intolerant, drinking the sugar may cause bloating, cramps, diarrhea and gas.

What might affect hydrogen breath test results?

Your child’s results could be affected if they:

  • 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
  • Use tooth paste the day of the test.

How do I prepare my child for a hydrogen breath test?

  • Stop taking antibiotics at least four weeks before the test.
  • The day before the test, do not feed your child high-fiber foods such as beans or whole-grain cereals. They should also avoid drinking carbonated beverages.
  • The child must fast (have nothing to eat or drink) for 12 hours before testing.
  • If your child smokes, it is important that they do not do so the day before testing.
  • Children should not exercise strenuously the day before testing.
  • The day of the test, your child should not brush their teeth two hours before the test begins.

Your child’s doctor may request additional dietary instructions. Be sure the doctor knows about all medicines, herbs, vitamins, and supplements your child is taking. This includes medicines that don’t need a prescription.

Lactose Intolerance

Lactose intolerance is a condition caused by a deficiency of an enzyme called lactase, which, in turn, causes the body to be unable to digest lactose, a sugar found in milk and milk products. Symptoms begin about 30 minutes to two hours after consuming foods or beverages containing lactose and can include nausea, cramps, bloating, abdominal pain, gas and diarrhea. A patient’s ability to tolerate lactose may change over time. Learn more about lactose intolerance and how it is treated at CHOC.