Hydrogen Breath Test for Lactose Intolerance

A hydrogen breath test provides information about the digestion of certain sugars or carbohydrates, such as milk sugar (lactose) or fruit sugar (fructose). This will help determine if you are intolerant to certain sugars. One example is the use of this test to detect lactose intolerance, a disorder in which people have symptoms due to the inability to digest lactose, a substance in many foods including milk and ice cream.

The test is also used for detecting abnormal growth of bacteria within the small bowel by having the patient ingest lactulose. Bacterial overgrowth can cause a variety of symptoms including diarrhea, bloating, gas, and abdominal cramps.

What to Expect

Knowing what to expect can help take the stress out of any procedure. Here's what you can expect with a hydrogen breath test.

A breath sample will be collected by having you exhale into a bag. You will then be given a solution of lactose, lactulose, or fructose to drink. You should drink this whole amount. Breath samples will be collected every 15 minutes. After each sample is collected, the sample will be removed from the bag with a syringe, allowing collection of another sample into the bag. During the test, you should take notice of your symptoms and inform the technician if you have your typical symptoms for which the test is being performed. During the test, you should not eat, chew candy, smoke, sleep, or exercise. When the test is over, generally after two hours or four hours, you may leave. You may return to your usual diet and activity after the test.

How to Prepare

Preparation for a hydrogen breath test begins four weeks before the procedure. Instructions may vary so you should check with your doctor or doctor's office to confirm your individual instructions. Instructions may include:

  • For four weeks before your test, do not take any antibiotics.
  • The day before your test, you will need to follow a restricted diet. You will be given a list of approved foods.
  • On the day of the test, you will need to have an empty stomach. You should not eat or drink anything for 12 hours before your test.
  • Your doctor may also recommend avoiding laxatives, stool softeners or bowel cleansing preparations for a period of time prior to your test.