In general, to ensure consistency of the glucose tolerance test, it is usually recommended to fast for about eight hours before the test, which means neither drinking nor eating. However, if the patient drinks water before having this test, it actually does not affect the results very much. The glucose tolerance test is mainly to assess the function of the pancreas to see if the blood sugar can be controlled to normal, or if the diagnosis of diabetes can be confirmed, as well as the diagnosis of abnormal glucose tolerance, and insulin secretion is mainly seen after meals, there will be a large dose of secretion, not eating before the glucose tolerance test, the impact is not very big. It is also possible to drink water after taking sugar water, but it is not recommended to exercise or eat excessively.