Hydrogen-Methane Breath Test

What is the Hydrogen-Methane Breath Test?

Hydrogen-methane breath testing is a noninvasive diagnostic test used to evaluate certain gastrointestinal conditions related to carbohydrate digestion and bacterial overgrowth. It measures the amount of hydrogen and/or methane in your breath after you ingest a specific sugar. Humans normally produce very little hydrogen and methane on their own. These gases are created when bacteria in the gut ferment carbohydrates that were not properly digested or absorbed. The gas enters the bloodstream and is exhaled through the lungs, where it can be measured.

When is Hydrogen Breath Testing Used?

1. Small Intestinal Bacterial Overgrowth (SIBO): When there is an overgrowth of bacteria in the small intestine, the test sugar may ferment prematurely and release hydrogen and/or methane gas.
2. Carbohydrate Malabsorption (such as sucrose, fructose, lactose): The test may show an inability to digest the carbohydrates in the small intestine. When this occurs, the sugar passes into the colon, where it ferments and releases hydrogen and/or methane gas.

Are there Side Effects of Hydrogen Breath Testing?

Side effects are usually mild and may include bloating, abdominal discomfort, gas, or diarrhea. These symptoms typically resolve shortly after the test is complete.

How do I Prepare for the Hydrogen-Methane Breath Test?

To ensure the most accurate results for your test, follow these instructions carefully and completely.

Twenty-four (24) hours before your test, you may only have the following foods:

• Baked or broiled chicken, turkey, or fish with salt and pepper seasoning only
• Plain, steamed white rice
• Eggs
• Tofu
• Clear chicken or beef broth
• You may use a small amount of olive oil for cooking
• Water only to drink
• You must follow this diet to ensure an accurate test.

Other important instructions:

• Twelve (12) hours before your test: Do not eat or drink anything except water. You may take your oral medicines with water unless otherwise instructed.
• Do not smoke or be exposed to second-hand smoke at least one (1) hour before and at any time during the test.
• Do not sleep or do any vigorous exercise for at least one (1) hour before your test.
• Inform your health care provider in advance if you have recently taken antibiotics. You will need to stop all antibiotics four (4) weeks before your test.
• Additionally, other medications you will need to hold include:
  • Stop probiotics two (2) weeks before your test.
  • Stop antimicrobial herbs (such as garlic, ginger, oregano, or elderberry) one (1) week before the test.
  • Stop laxatives three (3) days before the test.
  • Stop fiber supplements three (3) days before the test.
  • Stop digestive enzymes two (2) days before the test.
• Inform your health care provider in advance if you have had a recent colonoscopy. Your test should be scheduled at least three (3) weeks after.
• Inform your care provider if you have experienced new or worsening diarrhea.
• If you have diabetes and take insulin, speak with the provider who prescribes your insulin about reducing the dose on the day of the exam.

What Happens During the Hydrogen Breath Test?

• Depending on the reason for the test, you will drink a small amount of a test sugar (such as lactose, sucrose, fructose, or glucose).
• You will breathe into a collection bag at scheduled intervals for three (3) hours.
• A member of the healthcare team will collect these breath samples and analyze them using specialized equipment. The results will then be sent to your provider for interpretation.
• Please bring reading materials or your electronic devices - you will be in the procedure area for about three (3) hours.

What Happens After the Hydrogen Breath Test?

• You may return to your normal diet and activities after the test. Your healthcare provider will contact you with your results and discuss treatment recommendations.

How do you get to your test?

If you are being seen at National Jewish Health, please check in at the Front Desk. The test will take place in the MIDC (Minimally Invasive Diagnostic Center). If you have questions, please call 303-270-2424. If you need to reschedule, please call 303-398-1355, option #4.

© National Jewish Health, rev 2026