The small bowel bacterial overgrowth is characterized by the presence of colonic flora in the small bowel, may to lead malabsorption and/or diarrhea and/or weight loss. The small-bowel culture has served as the "gold standard" for diagnosing bacterial overgrowth. The colonic flora is able to ferment carbohydrates that are present in the lumen of the intestinal tract with production of hydrogen, which is subsequently observed and excreted by the breath. Therefore, the hydrogen breath test after oral carbohydrates administration represents an alternative, non-invasive and specific method for diagnosing small bowel bacterial overgrowth.