What is the exhaled hydrogen Test?

The hydrogen- based breath tests are a group of non-invasive, painless tests which allow to diagnose bad absorption of certain substances (mainly complex carbohydrates, like lactose, sacarose, sorbitol and fructose), as well as rule out the diagnosis of intestinal bacterial overgrowth.

These test are carried out measuring hydrogen present in exhaled air after taking a carbohydrates load, which is the reflex of the amount of hydrogen formed by the intestinal flora.

These tests are performed at the doctor´s office, being painless and lacking health risks. Nevertheless, if the patient is intolerant, several mild symptoms might be noticed (bloating, diarrhea or abdominal distension, among others). These symptoms are a manifestation of the carbohydrate intolerance itself, and usually passes by a few hours later.

The tests consist of blowing in a machine at a regular time intervals after the intake of a measured dose of a certain sugar. The duration of the test will be determined according to the type of carbohydrate intolerance to be measured. The maximum duration of the test if 4 hours in selected cases. It is mandatory that the test is performed after the patient have meticulously fulfilled a few instructions:

Test preparation

  • Antibiotics, aspirin, laxatives, probiotics or prokynetic drugs should be withdrawn at least four weeks before the test. It is also recommended to perform the test at least four weeks after a colonoscopy or a bowel preparation have been performed. Nevertheless, all of the above are not complete contraindications, and interpretation of the results will be done with the knowledge of the previous conditions.
  • 24 hours prior to the test the patient should have carried out a sugar and starch free diet. The day of the test the patient should have fasted for at least 8 hours prior to the test (drinking wáter is allowed).
  • The day of the test the patient should not smoke neither prior nor during the test procedure. The same way, the patient should not take chewing gums or sweets during the day of the test. It is also not allowed to smoke prior or during the test.
  • Intense physical exercise should be stopped at least 6 hours prior to the test. During the test it is also recommended to remain seated.
  • The patient should come to the office without having brushed teeth and without having used toothpaste, although it is recommended to take Clorhexidine rinsing at home before coming to the office.

Dieta sin hidratos de carbono 24h antes de la prueba.

  • Huevos (tortilla francesa, huevo duro o frito).

  • Arroz blanco (sin ajo, cebolla ni salsa de tomate).

  • Embutidos no elaborados (jamón serrano o ibérico).

  • Carne, pescado blanco o azul.

  • Agua, té, infusiones sin azúcar.
  • Leche y productos lácteos (yogures, quesos, mantequillas).
  • Cereales, pan, galletas, tostadas, biscotes, tortitas.
  • Productos de pastelería o bollería (magdalenas, donuts), dulces (caramelos, chicles) y mermeladas.
  • Legumbres, patata, verduras y vegetales.
  • Frutas y zumos de fruta.
  • Refrescos.
  • Embutidos elaborados (jamón cocido, pavo, mortadela, fuet, salchichón etc.).
  • Frutos secos.
  • Azúcar blanco o moreno ni edulcorantes.

Test preparation (pdf)

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