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What is a Hydrogen Breath Test?
A hydrogen breath test can be used to diagnose two conditions:
- An overgrowth of bacteria in the small bowel.
- A condition where the dietary sugar lactose, which is found in dairy products, is not ingested normally (lactose intolerance)
Both conditions may cause abdominal pain, bloating, gas, and diarrhoea.
Intestinal bacteria are present in the large bowel or colon of healthy people and can convert sugar to hydrogen. Some of this hydrogen is absorbed through the intestines into the blood stream, where it is transported to the lungs and exhaled in the breath during normal breathing.
What are the Benefits?
For investigation of small bowel bacterial overgrowth, the results of the test will guide your doctor on how best to treat your symptoms.
What are the Risks?
There are no significant risks associated with this test but patients who are found to be positive of either lactose intolerance or bacterial overgrowth of the small bowel may experience some gastrointestinal symptoms such as bloating and diarrhoea.
Is the Breath Test Reliable?
Hydrogen alone, methane alone or both gases simultaneously might be found in breath small samples. That is why it is important to always determine both gases in the breath samples. There are several advantages of hydrogen and methane breath tests. They are non-evasive, non-toxic, and relatively easily available and performed at a low cost.
How Shall I Prepare for the Test?
- You need to fast at least 14 hours before the test and not drink anything apart from water (particularly avoid milk and fruit juice the day before the test).
- Do not take antibiotics for four weeks before the test. Do not discontinue any medication without consulting your doctor.
- Avoid high fibre foods the day before the test. These include fruit and vegetables, wholegrain, beans, pasta, cereals and try to base meals around white bread, plain white rice, potatoes (skin off), chicken or fish.
- Your last meal on the day before the test should not be too big and should ideally not consist of any roughage (e.g., beans, cabbage, or leeks).
- You must not smoke/vape or chew gum 12 hours before the start of the test.
- Avoid laxatives for 3 days before the test (especially lactulose).
- Medicines (apart from vitamins, laxatives, and antibiotics) can be taken with pure water on the day of the examination.
- If you use dentures, do not use an adhesive on the day of the test.
- Make sure to brush your teeth on the day of the test and bring your own toothbrush and toothpaste with you.
How Long Will the Test Take?
Glucose breath test for investigation of small bowel bacterial overgrowth takes between 2 to 2.5 hours.
When Will I Know the Results?
A report with the results of the test and their interpretation will be sent to the requesting doctor within 5 working days.
What Does the Test Involve?
- You will be asked to give an initial breath test to make sure your stomach is empty. This is done by holding your breath for 15 seconds and then blowing gently and completely into a handheld gadget.
- A cup of sugar dissolved in water will be then given to you to drink.
- You will be asked to blow into the handheld machine every 20 minutes.
- During the test, you should not eat, chew gum, smoke, sleep, or exercise.
- You can continue normal activities after the breath sampling.
- The test will last 2-3 hours.
If your initial breath test reading indicates your stomach is not sufficiently empty, the test can’t continue. If this happens, you will be asked to come back and do the test again.
The Breath Test Procedure
The test involves blowing into a machine through a small tube. After an initial sample has been taken, you will be given a sugary solution to drink. Following this, further samples will be taken depending on the type of breath test you are having.
Glucose hydrogen breath tests for investigation of small bowel bacterial overgrowth – samples will be taken every 15 minutes for 2 hours.
Contact us
If you have any queries relating to this information, please contact the Endoscopy service.
About this information
Service:
Endoscopy
Reference:
H/081
Approval date:
13 October 2023
Review date:
1 October 2026
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Important note
This page provides general information only. It is developed by clinical staff and is reviewed regularly every 3 years for accuracy. For personal advice about your health, or if you have any concerns, please speak to your doctor.