Hydrogen Breath Testing

What is Hydrogen Breath Testing?

Hydrogen breath testing is a simple, needle-free test that can help explain some of the causes of belly pain, gas, bloating, or diarrhea. Your child breathes into a small bag or machine, drinks a sugar solution, then gives more breath samples over a few hours. The test measures gases in the breath — usually hydrogen and sometimes methane. High levels can mean certain sugars are not absorbed well or that extra bacteria are present in the small intestine.

Hydrogen breath testing can help diagnose:

• Sugar intolerance such as lactose or fructose malabsorption. These can cause pain, gas and loose stools after eating certain foods.
• Small intestinal bacterial overgrowth (SIBO) or related overgrowths, where bacteria ferment sugars and make extra gas.

How Does the Test Work?

Your child gives a baseline breath sample. Then your child drinks a measured sugar drink like lactose, fructose, glucose or lactulose. Breath samples are collected on a schedule — often every 15 to 60 minutes — for 2 to 4 hours. If the numbers rise in a clear pattern, it suggests the sugar was fermented by bacteria instead of being absorbed in the small intestine. A pediatric technician guides every step.

How to Prepare for Hydrogen Breath Testing

Good preparation makes results more accurate. Your care team will give exact instructions, which often include:

• Fasting for a short time before the test
• Avoiding antibiotics for a period before testing
• Skipping gum, candy and vigorous exercise right before and during the test
• Eating a simple meal the night before, if advised

Tell us about all medicines and supplements your child takes so we can advise what to pause.

What to Expect on Test Day

Plan to be in the clinic for 3 to 4 hours. A technician shows your child how to use the mouthpiece and collection bags or machine. After the sugar drink, breath samples are taken on schedule while your child rests, reads or watches a tablet. There are no needles. Most children return to normal activity the same day. A GI provider will then review the results with you and will explain next steps such as diet changes, medicines or other tests. It is most likely that it will take 3-5 days for the results to be analyzed and reported to you.

Safety and Limits

Hydrogen breath testing is safe and well tolerated. Some children may feel mild bloating or cramps from the sugar drink. The test does not explain every cause of abdominal symptoms. We interpret results in the context of your child’s history, exam and other studies to make a clear plan.

Why Nationwide Children’s Hospital?

At Nationwide Children’s, hydrogen breath testing is performed in our Neurogastroenterology and Motility Disorders Center — a high-volume pediatric program focused on complex motility and gut-brain conditions. Families travel from across the country and around the world for our expertise. Your child’s testing is coordinated by a team that includes pediatric GI, psychology, nutrition and nursing. We use child-friendly equipment and streamlined scheduling so you can move from testing to answers quickly. Most important, we turn results into a practical plan — from nutrition to medicine — to help your child get back to everyday life.