Diagnosis
To assess lactose intolerance, intestinal function is challenged by ingesting more dairy products than can be readily digested. Clinical symptoms typically appear within 30 minutes, but may take up to two hours, depending on other foods and activities. Substantial variability in response (symptoms of nausea, cramping, bloating, diarrhea, and flatulence) is to be expected, as the extent and severity of lactose intolerance varies among individuals.
It is important to distinguish lactose intolerance from milk allergy, an abnormal immune response, (usually) to milk proteins. This may be done in diagnosis by giving lactose-free milk, producing no symptoms in the case of lactose intolerance, but the same reaction as to normal milk if it is a milk allergy. An intermediate result might suggest that the person has both conditions. However, since lactose intolerance is common (some degree of it being found in most adults worldwide), it is not considered a disease and a medical diagnosis is not normally required. However, if confirmation is necessary, four tests are available.
Read more about this topic: Lactose Intolerance