Hydrogen gas in the body is produced from intestinal bacteria. Bacteria, normally in the large intestine, produce hydrogen through fermentation of carbohydrates- such as lactose, lactulose and fructose, causing gas, bloating, abdominal discomfort or diarrhea. Substrates containing these carbohydrates are given orally to test for small intestinal bacterial presence. Some of the hydrogen produced by the bacterial fermentation is absorbed by the intestinal mucosa whereby it enters the vasculature and is transported to the lungs.  Hydrogen is then exhaled by the lungs through normal breathing.  This is collected in a bag for computerized analysis.

In Small Intestinal Bacterial Overgrowth (SIBO), bacteria exist in the small intestine. The non-absorbable lactulose is metabolized on its way down showing a rise in hydrogen. If lactose is given as the challenge dose, bacteria compete with the natural digestive process before it is absorbed, and may produce an early rise in breath hydrogen as well.

In lactose intolerance, the individual has a deficiency in lactase, the enzyme that breaks down lactose.  Normally, lactose is broken down in the small intestine by lactase and very little lactose reaches the large intestine, where the bacteria could break it down to produce hydrogen.  In lactose intolerance (lactase deficiency), lactose is metabolized by colonic bacteria producing a large amount of hydrogen which is measured distally in the breath sample.

- Have your physician call Scheduling at 410.955.4166 to order the study
- No laxatives for at least a week
- No antibiotics for 4 weeks since it can affect the test
- Avoid slow digesting foods like beans and some other vegetables the day before
- Eliminate foods high in carbohydrates like bread or pasta
- You may have an early dinner of rice and meat or chicken
- Nothing to eat for 12 hours before your scheduled study
- Do not smoke, sleep or exercise vigorously ½ hour before or anytime during test.