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Department of Internal Medicine

Department of Internal Medicine

Diagnostic services

Patient instructions for hydrogen breath test

Hydrogen breath test may be used to diagnose the malabsorption of specific carbohydrates. Sugars malabsorbed in the small bowel are metabolised by colonic bacteria with the production of hydrogen, which diffuses rapidly across the colonic mucosa into the blood and can be measured in the breath. Patients drink a solution of lactose, fructose, sucrose or glucose in water. After drinking the solution, patients are asked to breathe into a plastic bag; breath samples are obtained every 30 minutes and analyzed for hydrogen content to determine if there is a proper break down of lactose or sucrose, or if there is evidence of bacteria overgrowth.

You must be off antibiotics and Pepto-Bismol for two weeks. On the evening before your test, you may have the usual amounts of meat and vegetables from dinner time until midnight. Please consume only small amounts of sugar and starch. After midnight, have nothing to eat or drink until your examination is completed.

More information about this procedure is available here.