Hydrogen (H2) exhalation tests

Hydrogen (H2) exhalation tests are gastroenterological tests that help make a diagnosis without device intervention, based on changes in the amount of hydrogen released in the patient’s exhaled air. Exhalation tests require the consumption of a special liquid containing lactose, fructose, or lactulose, which triggers a change in the composition of the exhaled air, which confirms the condition.

The hydrogen exhalation test can also be used to diagnose lactose sensitivity, small intestinal bacterial overgrowth syndrome (SIBO) caused by colon bacteria, and impaired fructose absorption.

Lactose intolerance, also known as lactose sensitivity, is a condition in which the body is unable to digest lactose in the diet in the absence of the enzyme that breaks down lactose.

Lactose is a complex sugar that requires the enzyme lactase produced in the small intestine to break down the lactose molecule into simple sugars that the body can utilize.

Lactose intolerance is not really a disease, but an evolutionary state, as adult mammals no longer need to digest lactose. As a result, in humans, the production of the enzyme that breaks down lactose decreases significantly with age after the breastfeeding period, it is a result of a gene variant that it persists in some people.

A larger part of the Hungarian population can digest lactose, among the Hungarian population approx. 60-65% are lactose tolerant and 35-40% are lactose sensitive.

It is important to highlight that lactose sensitivity is not the same as food intolerance caused by lactalbumin. A separate laboratory package is available to investigate complaints after consuming milk, including lactalbumin allergy and food intolerance. However, complaints require a gastroenterological examination in all cases, you should avoid self-diagnosis because the symptoms can be caused by several diseases.

The diagnosis of lactose sensitivity is most often made with the H2 breath test, during which the hydrogen content of the air exhaled by the patient is examined at certain intervals after consuming a lactose-containing beverage. In the case of lactose sensitivity, after consuming lactose, the hydrogen content of the exhaled air increases significantly, as the lactose, which is broken down in the intestine, produces hydrogen gas, part of which is absorbed into the bloodstream and exhaled through the lungs.

The lactulose hydrogen exhalation test is used to detect the presence of bacteria from the colon that have abnormally multiplied in the small intestine. This condition is known as small intestinal bacterial overgrowth syndrome (SIBO), which is associated with bloating, abdominal pain, diarrhoea, constipation, and early fullness.

Bacteria that enter the small intestine break down undigested carbohydrates, resulting in the production of hydrogen and methane gas, which also becomes measurable in exhaled air.

The fructose hydrogen exhalation test can be used to examine fructose malabsorption. As a result of the malabsorption, fructose enters the colon in undigested form, where it begins to ferment, leading to increased gas production. This causes unpleasant abdominal symptoms (bloating, diarrhoea cramps).

• Prior to the examination, it is necessary to consume lactose, fructose, or lactulose-containing liquid to detect the examined disease.
• A mouthpiece is connected to the sensor inlet, through which the patient blows exhaled air into the device.
• The total duration of the test is 120 to 180 minutes, the patient is required to blow into the device every 20 minutes for measurement.
• The test measures and displays the H2 content of the exhaled air.
• The test is simple, fast and painless.

• Stop taking antibiotics and probiotics 4 weeks before the test
• At least 4 weeks have to pass between endoscopic procedures/surgeries and H2 exhalation test
• Do not eat fruits and vegetables the day before the test, avoid hazelnuts and oilseeds
• Do not consume milk or dairy products the day before the test
• Do not drink alcohol and carbonated beverages the day before the test
• Stop smoking the day before the test
• On the day of the test, come with an empty stomach, take only the necessary medications
• Do not use toothpaste, mouthwash, chewing gum or candy on the day of the test