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Hydrogen breath test

What does it consist of?

Intestinal bacteria release hydrogen as they break down sugars, which in turn is transferred into the bloodstream and into the lung, and expelled to the outside world through respiration. By measuring the concentration of hydrogen in exhaled air, we can detect digestive disorders by identifying disturbances in the digestion and absorption of specific sugars.


The test consists of measuring the amount of hydrogen in exhaled air after administering a substrate sugar. The procedure begins with a baseline measurement of exhaled hydrogen, where the patient blows into a device that analyses the composition of their breath. Substrate sugar is then administered and additional measurements are taken every 15 to 30 minutes over a period of 1 to 2.5 hours. The time interval and total duration of the test will depend on the type of digestive disorder to be studied.


At CreuBlanca, we offer the possibility of performing the exhaled hydrogen test in the consultation room or in the comfort of your own home.

Cases in which it is recommended

To whom?

This test is intended for people with symptoms of SIBO and lactose, sorbitol or fructose intolerances, such as:

  • Bloating or abdominal distension
  • Gas and flatulence
  • Diarrhoea
  • Abdominal pain
  • Nausea
  • Unintentional weight loss


If you have hereditary fructose intolerance, you should not take the exhaled hydrogen test.

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