Fasting blood glucose of thirteen plus millimoles per liter is very serious and has reached the diagnostic criteria for diabetes. Under normal circumstances, the average adult fasting blood glucose range is 3.9 ~ 6.1 mmol / L, pregnant women less than 5.1 mmol / L. Therefore, fasting blood glucose thirteen points more mmol per liter is very serious, has been much higher than the normal range, at this time you need to be highly suspicious of the examination of the patient may be suffering from diabetes mellitus, diabetes mellitus diagnostic criteria, including fasting blood glucose greater than or equal to 7.0mmol / L. Usually, fasting blood glucose more than thirteen millimoles per liter of patients need to do further oral glucose tolerance test, if this test 2 hours of blood glucose is greater than or equal to 11.1 mmol / L, can be diagnosed as diabetes. Secondly, the general blood sugar is only slightly elevated, can also be considered to be caused by physiological factors, such as eating 1~2 hours before the examination, a short period of strenuous exercise and so on. In summary, people with abnormal fasting blood glucose need to actively cooperate with doctors to improve other tests and clarify the specific causes.