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Breath Test

Medically reviewed by Last updated on Aug 31, 2022.

What do I need to know about a breath test?

A breath test measures the amount of certain gases produced in your digestive system. It may be done to diagnose conditions such as carbohydrate (lactose or fructose) intolerance, bacterial overgrowth syndrome, and H. pylori infection.

How do I prepare for a breath test?

Your healthcare provider will talk to you about how to prepare for this test. You may be told not to eat or drink anything after midnight on the day of your test. Your provider will tell you which medicines to take or not take on the day of the test.

  • Carbohydrate intolerance and bacterial overgrowth syndrome tests: Do not take antibiotics, probiotics, or medicines that contain bismuth 4 weeks before this breath test. Do not use laxatives or enemas within 3 days of your test. Avoid high-fiber foods and fiber supplements 24 hours before the test. Do not smoke, use an E-cigarette, or exercise for at least 1 hour before your test. Do not chew gum or use mouthwash before your test. You can brush your teeth and drink water before your test.
  • H. pylori infection tests: Do not take antibiotics or medicines that contain bismuth 4 weeks before this breath test. Stop taking proton pump inhibitors, such as omeprazole, 2 weeks before your test. You may need to stop taking histamine H2-blockers, such as cimetidine or ranitidine, 24 hours before your test.

What will happen during a breath test?

Your healthcare provider will ask you to breathe in deeply and then exhale into a container that looks like a bag. Then, you will be asked to drink a liquid. The gases in your breath will be measured again 15 to 30 minutes after you drink the liquid. Samples of your breath will continue to be collected every 15 to 60 minutes for 3 to 5 hours. If you are being tested for H. pylori infection, your breath may only be collected twice over 20 to 30 minutes. Do not sleep, smoke, or exercise during the test. This could affect your test results.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.