A national consensus guideline on the performance and interpretation of hydrogen- and methane-based breath tests for carbohydrate malabsorption, small intestinal bacterial overgrowth, and intestinal methanogen overgrowth.

Abdominal bloating, distension, excessive gas, abdominal pain, diarrhea and constipation are common symptoms that may arise from carbohydrate malabsorption, carbohydrate intolerance, small intestinal bacterial overgrowth (SIBO), intestinal methanogen overgrowth (IMO), or disorders of gut-brain interaction. Hydrogen- and methane-based breath tests are safe, noninvasive, inexpensive and widely used, but differences in indications, patient preparation, test performance and interpretation can lead to inconsistent diagnoses and management. At the recommendation of the Israeli Gastroenterology Association, a multidisciplinary panel of adult and pediatric gastroenterologists, neurogastroenterologists, dietitians, clinical nutrition specialists and heads of gastrointestinal laboratories reviewed the literature and reached consensus during 8 meetings. This guideline provides practical standards for breath testing in adults and children. The panel recommends simultaneous measurement of hydrogen and methane, structured symptom recording during testing, standardized pretest preparation, and cautious interpretation in settings that alter anatomy or orocecal transit time. Lactulose is recommended as the preferred substrate for SIBO/IMO testing, with glucose as an acceptable alternative. Carbohydrate malabsorption should be distinguished from intolerance by the presence or absence of typical symptoms during the test. The guideline also defines suspected hypersensitivity and highlights methane production as a cause of false-negative hydrogen-based carbohydrate tests. These recommendations are intended to harmonize breath test practice and reporting, and to support rational, test-directed treatment in adult and pediatric patients.