Hydrogen Breath Testing | Cary… | Cary Gastroenterology Associates

This test measures hydrogen in your breath to diagnose several conditions that can cause gastrointestinal symptoms. In humans, only bacteria are capable of producing hydrogen. The hydrogen is produced when lactose sugars are not being properly digested and metabolized, as well as fructose sugars not being absorbed in sufficient quantity. The test is also used to diagnose the growth of bacteria in the small bowel.


  • Do not eat or drink anything after midnight the night before your test
  • You may brush your teeth the morning of your test, but do NOT swallow the toothpaste, water, or mouth wash
  • Do not take morning medications prior to the test. Do bring them with you to take immediately after your test
  • Do not smoke for three hours prior to the test

Hydrogen Breath Testing Instructions

What To Expect

At the start of the test, the patient blows into a small bag or balloon. The amount of hydrogen is measured in this sample of breath. You will then ingest a small amount of the test sugar (lactose, sucrose, fructose, etc. depending on the purpose of the test). Additional samples of your breath are collected and analyzed for hydrogen every 15 minutes for up to five hours. Following the test you may experience the same mild effects of lactose or fructose intolerance: bloating, distention, or diarrhea.


There is very low risk of any side effects or complications with this test.

Your Health Matters

Book an appointment today at one of our office locations throughout the Cary, Raleigh, Holly Springs and Triangle region. We are committed to providing you with the most comprehensive quality of gastroenterology care.