The hydrogen breath test is a simple medical test that measures hydrogen gas levels (HO2) in the breath one exhale. Hydrogen breath test is used to help diagnose common digestive problems, including SIBO, IBS and lactose intolerance. Different versions of the test measure our digestion of different sugars. The results help doctors confirm or rule out certain specific causes of one’s digestive problems.
What does the hydrogen breath test diagnose?
Many different digestive conditions will cause abnormal hydrogen levels in our gut, which can then be measured in our breath. But when doctor suggests the hydrogen breath test, it’s usually to confirm or rule out one of two conditions:
- Intolerance to a specific sugar, such as lactose, fructose, sucrose or sorbitol — also called carbohydrate malabsorption. Lactose intolerance is the most common.
- Small intestinal bacterial overgrowth (SIBO). This is when helpful bacteria from our colon have moved into our small intestine, where they don’t belong.
In the process of diagnosing irritable bowel syndrome (IBS), both of these conditions must be addressed as possible contributing factors.
Test Details
How does the hydrogen breath test work?
If you’ve ever experienced gas in your belly from indigestion — the bloating and swelling like a balloon, the painful movement of the gas through our digestive system and the uncomfortable process of farting it out — that gas was likely at least part hydrogen. If there’s hydrogen in our body, only one thing causes it: anaerobic gut bacteria digesting sugars and carbohydrates in our gut. This process is called fermentation.
These bacteria are supposed to live in our colon, where they play an important role in digestion. But sugars and carbohydrates aren’t supposed to be a major part of their diet. In a healthy digestive system, the sugars and carbohydrates that we eat are predigested before they reach the bacteria in our colon. If they haven’t been fully digested by then, the anaerobic bacteria will digest them, converting them into gas.
The gas in our colon is absorbed into our blood and carried into our lungs, where it’s expelled through our breath. That’s how our breath can show what’s going on in our gut. The hydrogen breath test measures hydrogen levels in our breath after consuming a particular sugar. The amount of hydrogen, and how fast it’s produced, gives us information about how patient’s digestion is working.
Do breathe tests measure other gases?
- Methane: Because everyone’s assortment of gut bacteria is a little different, some people have more methane in their breath than hydrogen. For this reason, most clinics measure for both gasses at the same time. Both are measured in the same way. However, the methane test is more recent and may not be as accurate as the hydrogen breath test.
- Carbon dioxide: A different type of breath test measures carbon dioxide (CO2) levels in our breath. The H. pylori breath test is one. This test is separate from the hydrogen breath test because of what patient ingest during the test. While the hydrogen breath test measures patient’s digestion of sugars or carbohydrates, the carbon breath tests require patient to consume a solution of carbon molecules. The two tests are used separately to diagnose different gastrointestinal diseases.
What are the different types of hydrogen breath tests?
When a patient takes a hydrogen breath test, he/she’ll give a breath sample before and several after consuming a particular test sugar — usually lactose, fructose, sucrose, sorbitol, glucose or lactulose. The choice of sugar depends on what kind of condition a doctor is checking for. 
- Lactose, fructose, sucrose and sorbitol tests check for intolerance to those particular sugars. These are all sugars that, for different reasons, can be hard for some people to digest. Patient’ll only be tested for one at a time. If the breath test results in high levels of hydrogen, it means that sugar wasn’t well digested in this patient’s intestines.
- Glucose is the preferred sugar to test for small intestinal bacterial overgrowth (SIBO). That’s because glucose is usually very quickly absorbed in our small intestine. If glucose is being fermented by anaerobic bacteria and producing hydrogen, it means that too many of those bacteria have moved into patient’s small intestine, and they’re digesting the glucose before it has had a chance to be absorbed.
Preparation for the hydrogen breath test
Certain foods, medications and activities can alter the results of the hydrogen breath test. The doctor should ask his/her patient to follow some specific guidelines in the weeks, days and hours leading up to the test to maximize its accuracy.
- One month before: Ask your patient to stop taking antibiotics and probiotics, both of which can alter the normal balance of bacteria in his/her gut.
- One week before: Aske to stop smoking. Also stop taking any allopathic laxatives or allopathic fiber supplements, allopathic antacids and prokinetics, they affect the motility.
- One day before: Asked your patient to limit his/her diet to only low fiber, easily digested foods. Specific recommendations may vary, but the diet often excludes oils and fats, white sugar and sweeteners and seasonings, dairy products and grains, except for white bread and white rice. Baked or boiled fish or poultry (not broilers) with salt and pepper are safe bets.
- On the day of the test: Ask your patient to fast for 12 hours. That means no food no water, also avoid exercising or sleeping within a few hours of the test.
What should a patient expect during the hydrogen breath test?
Patient’ll give his first breath sample by breathing into a breathalyzer machine, which often looks like an inflatable bag with a tube attached. Then, patient will drink the sugar solution. After consuming the sugar, the patient will continue to give breath samples for the next few hours, at intervals of about 15 to 30 minutes.
Patient may also be asked to record his digestive symptoms resulting from the test sugar — any abdominal pain, bloating, farting, etc. Physical activity should be limited during the test.
Are there any risks or side effects to the hydrogen breath test?
The hydrogen breath test is noninvasive and generally harmless, but it does identify digestive problems by inducing those problems. So, while breathing into a bag might be painless in itself, ingesting the test sugar may well result in some abdominal discomfort — the same kinds of discomfort that made patient seek medical care in the first place. Hopefully, the test will help isolate the underlying cause of your patient’s symptoms.
Results and Follow-Up
How do we interpret the results of hydrogen breath test?
Hydrogen levels are measured in parts-per-million (ppm). Normal hydrogen values in a healthy 
digestive system are less than 16 ppm. If patient’s baseline level is more than 16 ppm on the day of the test, ask your patient to go back on the pre-test diet and try again another day.
If the carbohydrate malabsorption is raised of more than 20 ppm over the baseline is considered a positive test. For SIBO testing, the rise in hydrogen by 20 ppm above the baseline must occur within 90 minutes, as hydrogen is being fermented in patient’s small intestine instead of in his/her colon.
How accurate or reliable are results of the hydrogen breath test?
There are a few complicating factors that can muddle results from the test. If patient didn’t follow the protocol leading up to the test — for example, if patient took antibiotics or laxatives, or didn’t fast — the test results might not be accurate. If present patient is one of those people (about 15% to 30%) whose gut bacteria tend to produce methane more than hydrogen, this may affect the results.
You can be sure that the hydrogen resulted from poor digestion of the test sugar if your patient does have a positive result from the hydrogen breath test. Tests for specific sugar intolerances and the glucose test for SIBO are very reliable for diagnosing those conditions.
Sometimes, those conditions might not fully explain all of patient’s symptoms, or treating those conditions might not fully cure patient’s symptoms, further testing might be needed to identify other factors causing them or implement other dietary changes or treatments that might help improve them.
P. S: This article is only for doctors having good knowledge about Homeopathy and allopathy, for learning purpose(s).
For proper consultation and treatment, please visit our clinic.
Dr. Sayyad Qaisar Ahmed (MD {Ukraine}, DHMS), Abdominal Surgeries, Oncological surgeries, Gastroenterologist, Specialist Homeopathic Medicines.
Senior research officer at Dnepropetrovsk state medical academy Ukraine.
Location: Al-Haytham clinic, Umer Farooq Chowk Risalpur Sadder (0923631023, 03119884588), K.P.K, Pakistan.
Find more about Dr Sayed Qaisar Ahmed at:
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