Hydrogen breath test

This information from Great Ormond Street Hospital (GOSH) is about having a hydrogen breath test.

A hydrogen breath test is a way of measuring whether your child is intolerant to certain substances, mainly different types of sugars.

What will happen?

At home

Your child should not have any of the following the day before the test:

  • onions
  • leeks
  • cabbage
  • beans
  • pickled vegetables
  • chewing gum
  • vitamins
  • laxatives
Your child should not have antibiotics in the four weeks prior to the test. If they require antibiotics please contact the admissions coordinator to reschedule the test.

Your child should not have anything to eat or drink any milk or fruit juice for 14 hours before the test.

Your child should brush their teeth thoroughly the morning of the test.

At hospital

Your child will have a set of observations and their weight measured before the test starts.

They will be asked to blow into a handheld machine with one continuous breath for 15 seconds. Younger children will give a continuous breath into a mask over their mouth. It might be helpful to practise this at home beforehand.

Your child will then be given a drink.

For the next three to four hours they will continue to breathe into the machine every 15 to 30 minutes, staying as still as possible. Please bring some books or toys to occupy them for this period.

When the test is finished, they will be able to eat and drink – please bring in a favourite drink and snack.

Back home afterwards

We will discuss the results with you in clinic.

We will post you a clinic appointment.

Are there any risks?

The chance of any problems occurring is minimal but it is important that you are aware of them.

The test may give your child stomach ache, diarrhoea, dizziness or vomiting as we are giving them a large dose of a substance they do not usually tolerate. Please report any symptoms to the nurse performing the test so your child can be monitored.

Compiled by:
The Gastroenterology Investigation Suite in collaboration with the Child and Family Information Group
Last review date:
September 2019