Hydrogen Breath Test Explained

This is a test for bacterial overgrowth, or intolerances to lactose, fructose, or sucrose. Glucose is a sugar that will be broken down by bacteria if present in the small bowel with hydrogen or methane gas as a by-product. The breath sample will be analyzed for hydrogen or methane content to determine if you are able to properly break down the lactose, fructose, or sucrose, or if you have bacterial overgrowth.

Why Use a Hydrogen Breath Test

Commonwealth Laboratories, Inc. uses hydrogen breath testing in the diagnosis of two conditions

The first is a condition in which 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 the digestion of other sugars such as sucrose and fructose.
The second condition for which 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.

Either of these conditions may cause abdominal pain, abdominal bloating and distention, flatulence (passing gas in large amounts), and diarrhea.

A test frequently ordered by physicians is the hydrogen breath test for small intestinal bacterial overgrowth (SIBO.) Researchers studying digestive disorders have determined that a large number of patients suffering from abdominal pain, bloating, diarrhea, etc., were found to have this disorder.

Bacteria that are normally found in the large intestine had migrated into the small intestine. There appears to be a strong correlation between SIBO and IBS. Once diagnosed, and treated with an appropriate protocol of antibiotics, these patients have experienced welcome relief from their symptoms.

Similarly, accurate diagnosis of one or more of the sugar intolerances by using one of our breath test kits, can lead to development of a treatment plan that can greatly diminish painful digestive reactions to lactose, fructose, or sucrose.

The test is simple, non-invasive, patient-friendly and is performed after a short period of fasting (typically 8-12 hours).

What can I expect from a hydrogen breath test?

This test requires that you drink a solution of lactose, fructose, sucrose, or glucose in water. Lactose is the sugar found in milk and is normally broken down in the small bowel.

Glucose is a sugar that will be broken down by bacteria if present in the small bowel with hydrogen as a by-product. Sucrose is a common sugar found in foods such as candy. After drinking the solution, you will be asked to breathe into a plastic bag. Breath samples are obtained every 15 minutes for adults, and every 30 minutes for children.

The breath sample will be analyzed for hydrogen content to determine if you are able to properly break down the lactose or sucrose, or if you have bacterial overgrowth.

The test for glucose lasts about 2 hours and the tests for lactose, fructose, and sucrose last about 2 to 3 hours. The test is performed in the Gastrointestinal Physiology Laboratory of the Medical Procedures Unit.

How do I prepare for a hydrogen breath test?

Please follow these instructions to ensure a successful test.



TWO DAYS BEFORE your test:


THE DAY BEFORE your test:


DO NOT EAT, DRINK or SMOKE until your examination is completed.

This includes any type of GUM or CANDY.

Please note: breath tests can be done anytime before a colonoscopy prep; but not for four (4) weeks after a colonoscopy prep, or any test that requires a bowel prep.

Before starting the test you will be asked to rinse your mouth with mouthwash. This limits the effect of bacteria in your mouth on the results.

Can I take my medicine before a hydrogen breath test?

Critical medicines, such as those for your heart, blood pressure, breathing, or seizures, should be taken with sips of water on the morning of the procedure.

Noncritical medicines, including over-the-counter medicines and supplements should not be taken, unless your physician or nurse has advised you otherwise.

Re: Low carbohydrate diet


  • Foods containing added sugars
  • Desserts
  • Sugar-sweetened beverages
  • Pasta, breads, grains, cereals, potatoes
  • Milk and milk products

Focus on:

Proteins – including meat, eggs, poultry, fish.

Source & More Info: med.umich.edu and Hydrogen Breath Testing



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