Hydrogen/Methane Breath Test

The hydrogen/methane breath test is a test that uses the measurement of hydrogen in the breath to diagnose several conditions that cause gastrointestinal symptoms. In humans, only bacteria (specifically anaerobic bacteria in the colon) are capable of producing hydrogen. The bacteria produce hydrogen when they are exposed to unabsorbed food, particularly sugars and carbohydrates, not proteins or fats. Although limited hydrogen is produced from the small amounts of unabsorbed food that normally reach the colon, large amounts of hydrogen may be produced where there is a problem with the digestion or absorption of food in the small intestine, which allows more unabsorbed food to reach the colon.

Large amounts of hydrogen also may be produced when the colon bacteria move back into the small intestine, a condition called bacterial overgrowth of the small bowel. The bacteria are exposed to unabsorbed food that has not had a chance to completely travel through the small intestine to be fully digested and absorbed. Some of the hydrogen produced by the bacteria, whether in the small intestine or the colon, is absorbed into the blood flowing through the wall of the small intestine and colon. The hydrogen-containing blood travels to the lungs where the hydrogen is released and exhaled in the breath where it can be measured.

When Is Hydrogen Breath Testing Used?

The first condition for which hydrogen breath testing is used is when dietary sugars are not digested normally. The most common sugar that is poorly digested is lactose, the sugar in milk. Individuals who are unable to properly digest lactose are referred to as lactose intolerant. Testing also may be used to diagnose problems with digestion of other sugars such as sucrose, fructose and sorbitol.

The second condition for which hydrogen breath testing is used is for diagnosing bacterial overgrowth of the small bowel, a condition in which larger-than-normal numbers of colonic bacteria are present in the small intestine.

The third condition for which hydrogen breath testing is used is for diagnosing rapid passage of food through the small intestine.
All three of these conditions may cause abdominal pain, abdominal bloating and distention, flatulence (passing gas in large amounts) and diarrhea.

Are There Side Effects of Hydrogen Breath Testing?

The side effects of hydrogen breath testing are exactly what one would expect to see in people who poorly digest and absorb sugars and carbohydrates; for example, bloating, distention, pain and diarrhea. When the test sugar is used, these symptoms are unlikely to occur or are mild because the dose of the test sugar is small.

How Do I Prepare for the Hydrogen Breath Test?

To ensure the best results for your test, follow these instructions carefully and

  • Twenty-four (24) hours before your test, stop eating all grains (including pasta,
  • bread and cereals), all fruits, all vegetables including any products that contain corn, all nuts, seeds and beans, all dairy products (including cheese, ice cream, butter and yogurt) and all meats. You may have the following foods:
    • Baked or broiled chicken or turkey with salt and pepper only,
    • Baked or broiled fish with salt and pepper only,
    • Plain, steamed white rice,
    • Eggs, and
    • Clear chicken or beef broth and
    • Water only to drink.
  • Twelve hours before your test, you may have nothing by mouth, except water. You may take your oral medicines with water.
  • You must adhere to the above diet to ensure an accurate test.
  • You may not smoke or be exposed to second-hand smoke at least 1 hour before and not any time during the test.
  • You may not sleep or do any vigorous exercise for at least 1 hour before your test.
  • Inform your health care provider in advance if you have recently used antibiotics.
  • You will need to stop all antibiotics four weeks before you test.
  • Inform your health care provider in advance if you have had a recent colonoscopy.
  • Your test will need to be scheduled at least three weeks after a colonoscopy
  • Inform your health care provider if you are taking probiotics. You will need to stop taking probiotics 2 weeks before your test.
  • Inform your care provider if you have experienced new runny diarrhea.


What Happens During the Hydrogen Breath Test?

  • If you are diabetic and take Insulin, talk with the doctor who prescribes your Insulin about reducing the dose the day of the exam.
  • If you are diabetic, please bring your glucose meter, test strips, and a source of fastacting glucose with you (such as glucose tablets or glucose gel).
  • Take other medicines you normally take with a few sips of water.
  • Arrive for your appointment at the scheduled time:
  • Please bring reading materials or your electronic devices with you because you will be in the procedure area for about 3 hours.
  • Prior to hydrogen breath testing, you will fast for 8 hours. You will be instructed to blow up a balloon-like bag, completely filling it with air. The concentration of hydrogen is measured in a sample of breath removed from the balloon.
  • Depending on the purpose of the test, you will then drink a small amount of a test sugar (such as lactose, sucrose, sorbitol, fructose, or lactulose).
  • Then you will blow air into a bag every 15 minutes for up to 3 hours.
  • You may have small sips of water during the test, but nothing to eat.
  • You will not be allowed to sleep during your test.
  • The test sugar gets broken down in your body and measurements of hydrogen and methane will be obtained from your breath samples from the air you breathe into these bags. Normally, very little is detected in breath. However, hydrogen and other gases are produced when undigested lactose in the colon is fermented by bacteria.
  • Raised hydrogen breath levels indicate the improper digestion of lactose, which could lead to a diagnosis

What Happens After the Hydrogen Breath Test?

You may resume your normal activities and diet after a hydrogen breath test. You doctor will inform you of the test results.

How Do You Get to Your Test?

Please check in at the Front Desk. The test will take place in MIDC (Minimally Invasive Diagnostic Center). If you have questions, please call 303.398.1355. Also, if you need to cancel the appointment, please call.


This information has been approved by Miranda Y. Ku, MD, MPH and Renee Mondragon, RN, BSN (August 2014).