To assess lactose intolerance, it is only necessary to challenge the intestinal function by ingesting more dairy than can be readily digested, substantial variability of the clinical response (symptoms of nausea, cramping, bloating, diarrhea, and flatulence) are to be expected as the extent and severity of lactose intolerance varies between individuals. more

To assess lactose intolerance, it is only necessary to challenge the intestinal function by ingesting more dairy than can be readily digested, substantial variability of the clinical response (symptoms of nausea, cramping, bloating, diarrhea, and flatulence) are to be expected as the extent and severity of lactose intolerance varies between individuals. Clinical symptoms typically appear within 30 minutes but may take up to 1-2 hours depending on other foods and activities. In a hydrogen breath test, after an overnight fast, 50 grams of lactose (in a solution with water) are swallowed. If the lactose cannot be digested, enteric bacteria metabolize it and produce hydrogen. This can be detected in the air the patient exhales. The test takes about 2 to 3 hours. A medical condition with similar symptoms is fructose malabsorption. less