What Is the Hydrogen Breath Test Normal Range?

A hydrogen breath test is a diagnostic tool used to identify certain digestive conditions. It measures the levels of hydrogen and potentially methane gases in your breath. This test helps healthcare providers understand how your body processes certain sugars and whether there’s an imbalance in your gut bacteria.

Purpose of the Hydrogen Breath Test

The hydrogen breath test is performed to diagnose conditions like small intestinal bacterial overgrowth (SIBO) and carbohydrate malabsorption, which includes intolerances to sugars such as lactose, fructose, and sorbitol. In a healthy digestive system, most carbohydrates are absorbed in the small intestine. If they are not fully digested, they reach the colon where bacteria ferment them.

This fermentation process by anaerobic bacteria in the gut produces gases like hydrogen and methane. These gases are absorbed into the bloodstream and expelled through the lungs. An increase in hydrogen or methane can indicate that undigested sugars are reaching bacteria in the small intestine, as seen in SIBO, or that the body is not properly breaking down specific carbohydrates.

How the Test is Administered

The hydrogen breath test begins with a fasting period, usually 8 to 12 hours prior to the test. First, you provide a baseline breath sample by blowing into a collection device. Following this, you consume a specific sugar solution, such as lactulose, lactose, fructose, glucose, or sorbitol, depending on the condition being investigated.

After drinking the solution, breath samples are collected at regular intervals, every 15 to 30 minutes, for two to three hours. During this time, you should limit physical activity and avoid eating or drinking anything else. The collected breath samples are then analyzed for hydrogen and methane content to track changes over time.

Interpreting Normal and Abnormal Results

A “normal” baseline hydrogen level in a healthy digestive system is less than 16 parts per million (ppm). After consuming the sugar solution, a normal response involves minimal or no significant rise in hydrogen or methane levels. If your baseline hydrogen level is above 16 ppm, you might be asked to repeat the test after adhering more strictly to the pre-test diet.

For carbohydrate malabsorption, a rise of more than 20 ppm in hydrogen over the baseline is a positive result. In the case of SIBO, a rise of 20 ppm or more in hydrogen, or 10 ppm or more in methane, within the first 90 minutes of the test, indicates bacterial overgrowth in the small intestine. For glucose-based SIBO tests, an increase of 12 ppm or more in hydrogen and/or methane suggests bacterial overgrowth. A healthcare professional interprets these results in conjunction with your symptoms and medical history.

Preparing for Your Test

Accurate hydrogen breath test results depend on careful preparation. You must stop taking certain medications weeks before the test; for instance, oral antibiotics should be discontinued for at least four weeks, and probiotics, laxatives, and anti-diarrheal medications for about one week prior. Discuss all your medications with your doctor, especially if you have diabetes, as insulin dosages might need adjustment.

The day before the test, you will need to follow a strict low-fiber or low-carbohydrate diet, avoiding foods like whole grains, fruits, vegetables, and dairy. Examples of permitted foods include plain white rice, white bread, baked or broiled chicken or fish (seasoned only with salt and pepper), eggs, and clear broth. A fasting period, 12 hours, is required immediately before the test, with only water allowed. Additionally, avoid smoking, chewing gum, using mouthwash, or engaging in vigorous exercise on the day of the test.

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