Lactose breath test

Do you experience nausea, abdominal cramps, bloating, excessive flatulence or diarrhea after consuming milk and/or dairy products? If so, you may be lactose intolerant.

Lactose is a type of sugar found in milk and dairy products. Normally, lactose is broken down in the small intestine, thanks to the enzyme lactase. Patients with lactose intolerance have a deficiency of this enzyme, meaning that the lactose is not properly broken down. This makes the lactose go to your colon where it produces gas. This gas is then absorbed into your blood, passes through your lungs and is exhaled. If there is a lot of this gas in your exhaled air, it could mean that your body is not absorbing lactose properly (lactose malabsorption).

This study is perfectly safe, including for pregnant women and children.

• At the start of the test, you need to exhale through a mouthpiece into a measuring device. This determines the basic hydrogen level of your breath before ingesting lactose.
• After this, you ingest the test substance: 25g of lactose dissolved in 2 glasses of tepid water. You will not be administered any radioactive products. The tests do not carry any other risks.
• You will then inhale through the mouthpiece and into the measuring device every fifteen minutes.
• The test lasts three hours. During the test, you stay sitting quietly. You may not walk around, nor eat or drink. So, feel free to bring some reading material.
• If you are lactose intolerant, you may experience abdominal cramps, nausea, etc. during the test. This is normal, since you were administered a fairly high dose of lactose.
• At the end of the test, you will be informed of the result.

It is important to follow these guidelines. This way, we avoid erroneous results:

• Starting four weeks before the test:
  No antibiotics may be taken and no colonoscopy may be performed
• Starting one week before the test:
  No anti-reflux medication and acid blockers may be used
• Starting three days before the test:
  No laxatives, especially lactulose
• The day before the test :
  • Avoid milk and fruit juice
  • Avoid high-fibre foods
• Last meal:
  Have a light meal, low in fibre and without dairy products
• Twelve hours before the test:
  • Be fasting (do not eat or drink)
  • No smoking nor chewing gum
• Day of the test itself:
  • No vitamins, laxatives or antibiotics.
  • Continue taking your normal medication (anticoagulants, blood pressure and cholesterol medications) just as you do regularly every day
  • Brush your teeth thoroughly before the test with clean water (no toothpaste) Do not use any denture adhesive the day of the test
  • Drink a glass of warm water in the morning to promote bowel movement and eliminate bacteria from your intestines

If you have diabetes, it is best to consult your physician beforehand.

Latest publication date: 16/05/2024
Supervising author: Dr Monsaert Els