ABOUT THE TEST The test consists of administering a glucose solution orally and collecting the exhaled air at different times. (each 30 minutes), to determine the amount of hydrogen and/or methane exhaled through the breath. The total duration of the test is 3 hours and a half (210 minutes). Under normal conditions, glucose is absorbed in the small intestine.. If there is insufficient absorption of glucose due to a deficiency in its intestinal transporter, This reaches the large intestine where it is fermented by resident bacteria., producing gases (hydrogen and/or methane) which are partially absorbed by the blood and expelled through the breath. Thus, according to results obtained from expired hydrogen and/or methane for each intake, we can detect a possible glucose intolerance. To interpret the results you should go to a specialist who knows your clinical situation., This being essential in the event that any of the results are positive.