How to prepare for hydrogen breath test

To prepare for hydrogen breath test, avoid antibiotics 4 weeks before the test. Avoid laxatives 1 week before the test. Hydrogen breath test is used to diagnose lactose and fructose intolerance as well as small intestinal bacterial overgrowth (SIBO).

What is hydrogen breath test?

Breath test is the measurement of gases produced in the intestine and expired through the lungs. Intestinal gases come from four sources. These are swallowed air and air mixed with food, gases from the blood to the intestine, chemical reaction in the gut, and gases from gut bacteria. Normal people have 30-200 cc (100 cc on average) of Intestinal gas.

These gases are hydrogen (H2), carbon dioxide (CO2), methane (CH4), oxygen (O2), nitrogen (N2), hydrogen sulfide (H2S), indole, skatole and ammonia (NH3). Hydrogen and methane are produced only through gut bacteria metabolism. They are the gases measured during hydrogen breath test.

Why do you need hydrogen breath test

  • Diagnose abnormal absorption of carbohydrates like lactose and fructose.
  • Evaluate bloating.
  • Diagnose small intestinal bacterial overgrowth (SIBO).
  • Evaluate chronic constipation especially slow-transit constipation and other gastrointestinal symptoms.
  • Investigate abdominal cramps, diarrhea and excessive flatulence.

How long does the study lasts

The test lasts two to four hours.

How do I prepare for the hydrogen breath test 

  • Avoid antibiotics for 4 weeks prior to the breath test.
  • Stop pro motility drugs and laxatives one week prior to breath testing. These are loperamide (Imodium), diphenoxylate and atropine (Lomotil), senna, milk of magnesia, bisacodyl (Dulcolax), polyethylene glycol (Miralax), lubiprostone (Amitiza), linaclotide (Linzess), plecanatide (Trulance), erythromycin, azithromycin (Zithromax), metoclopramide (Reglan), domperidone (Motilium). Do not do any test that requires bowel cleansing like colonoscopy or barium enema.
  • Avoid fermentable foods such as complex carbohydrates the day before your breath test. These include pasta, beans, fiber cereals, and high fiber foods. Avoid soda and cola drinks. Avoid butter and margarine. You can have plain white bread, plain white rice, plain white potatoes, baked or broiled chicken, fish, and water. Non-flavored black coffee or tea is allowed.
  • Do not eat or drink 12 hours before your test. You may use your essential medications with sips of water. If you have diabetes mellitus and take insulin, your insulin dose will be adjusted. Do not take short-acting insulin while you’re fasting.
  • Avoid smoking or chewing tobacco on the day of the breath test.
  • Brush your teeth 2 hours before the test.
  • Do not chew gum, or eat breath mints or candy before or during the test.
  • Do not exercise or sleep during the test.


How to ensure accurate results

  • The correct dose of lactulose for breath testing is 10 g with or followed by one cup of water.
  • Dose of glucose for breath testing is 75 g mixed with or followed by one cup of water.
  • The correct dose of lactose for breath testing is 25 g mixed with or followed by one cup of water.
  • Dose of fructose for breath testing is 25 g mixed with or followed by one cup of water.
  • Fructose and lactose breath testing should be performed for at least 3 hours.
  • The presence of bacterial overgrowth should be ruled out before performing lactose or fructose breath testing.
  • Hydrogen, methane and carbon dioxide should all be measured simultaneously during breath testing.


What to expect during the procedure

  • The nurse or technician will verify your name and procedure.  She will confirm that you are fasting.
  • Breath samples are collected by having you exhale into bag.
  • A solution of glucose, lactose, lactulose, or fructose will be given to you to drink. Drink everything.
  • Inform the nurse or technician if you have any symptoms during the test.
  • Breath samples are collected every 15 or 30 minutes. After each sample is collected, it is removed from the bag with a syringe. This allows collection of another sample into the bag.

What to expect after the procedure

You do not need a driver to take you home because anesthesia is not used during the test. Resume regular activities after this. You can eat and take your medicines.

Your doctor will notify you of the results.

Interpretation of breath test results

  • A rise of ≥20 p.p.m. from baseline in hydrogen during the test should be considered positive for fructose and lactose breath testing.
  • Rise of ≥20 p.p.m. from baseline in hydrogen by 90 min should be considered a positive test for SIBO.
  • Two peaks on breath test are not required for the diagnosis of SIBO.
  • A level of ≥10 p.p.m. be considered positive for methane on a breath test.


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