Blood glucose and glucose tolerance are two different concepts, the main differences are as follows: First, the definition is different, blood glucose is the concentration of glucose in the blood. The normal value of fasting blood glucose is 3.9-6.0mmol/L. Glucose tolerance is the examination of oral glucose tolerance test, which is the ability of the body to bear the glucose load. Second, the check is different, blood glucose is drawn venous blood check, there are fasting blood glucose, postprandial blood glucose and random blood glucose. Glucose tolerance is 75 grams of glucose orally, respectively, before serving sugar, one hour after serving sugar and two hours after serving sugar to extract venous blood to determine blood glucose, insulin can be measured at the same time. Third, the role of different, blood glucose can be used for the diagnosis of diabetes, but only on behalf of the instantaneous blood glucose. Oral glucose tolerance test is the gold standard for the diagnosis of diabetes mellitus, also used for the diagnosis of gestational diabetes mellitus and the determination of pancreatic islet function, which is more reliable than blood glucose in diagnosing diabetes mellitus.