Understanding Hydrogen Breath Testing

What does hydrogen breath testing measure?

The hydrogen breath test measures hydrogen levels in your breath. It is used to diagnose several conditions that cause GI symptoms including SIBO, lactose intolerance, and fructose intolerance.

In humans, only bacteria, specifically, anaerobic bacteria fond in the large intestine (or colon) are able to produce hydrogen. Bacteria produce hydrogen through a process called fermentation when they are exposed to unabsorbed carbohydrates and sugars present in our GI tract.

A small amount of hydrogen is normally produced from unabsorbed food that reaches the colon, however this is minimal. Under healthy conditions, by the time food reaches the large intestine the majority of digestion and absorption has already been completed.

Large amounts of hydrogen may be produced when food is not digested or absorbed properly in the small intestine, and is allowed to reach the large intestine undigested. If carbohydrates are not absorbed properly or too many bacteria are present in the small intestine, a larger amount of hydrogen will reach the large intestine.

Hydrogen that bacteria in the gut produce is absorbed back into the bloodstream through the walls of the small and large intestine. This hydrogen-containing blood travels to our lungs, where it is released and exhaled in our breath. Elevated hydrogen levels tend to be associated with SIBO, IBS, and faster transit times of food through the digestive tract (as is the case in diarrhea or dumping syndrome).

How does hydrogen breath testing work?

Bacteria in the small intestine feed off of undigested carbohydrates from food sources, creating fermentation gases, specifically methane and hydrogen. SIBO breath testing measures these gasses.

To diagnose bacterial overgrowth and rapid transit through the small intestine, lactulose is used. Lactulose is a sugar that is not digested and absorbed by humans. You’ll be asked to drink a container of lactulose 1 hour before your schedule breath test. Then, you’ll come into our office and over the course of 3 hours you’ll be asked to intermittently breath into a machine. Levels of hydrogen present in your breath will be measured.

Lactulose will pass undigested through your small intestine and into your colon. With SIBO, we’ll notice two peaks in the hydrogen levels in your breath: one as the lactulose passes the bacteria in your small intestine and a second after it enters your large intestine.

Are there risks associated with hydrogen breath testing?

There are very few risks associated with breath testing. Patients may feel discomfort from ingesting lactulose. Diarrhea, gas, cramping or bloating may occur. Nausea and vomiting have been reported. Symptoms are usually transient.

How should I prepare for the test?

  1. The breath test should not be performed within 4 week of a colonoscopy or barium enema.
  2. You should not take any antibiotics or bismuth preparations (Pepto Bismol) within 2 weeks or having the breath test.
  3. Avoid laxatives, stool softeners and stool bulking agents for 1 week prior to the test.
  4. The day before the procedure avoid high fiber foods including beans, whole-wheat pasta, fruits, fiber or bran cereals, tofu, nuts, whole wheat and rye breads.
  5. On the day of the test:
    1. a. Do not eat or drink anything for 8 hours before the test.
    2. b. Avoid peppermint oil and all probiotics the day of the test.
    3. c. DO NOT eat, drink (except water), chew gum or tobacco, smoke cigarettes, eat breath mints or candy before or during the test.
    4. d. DO NOT sleep or exercise during the test.
    5. e. DO TAKE prescription medications.
    6. f. DO BRUSH your teeth prior to the test.

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