A high blood glucose of 13.9mmol/L may be caused by diabetes, stress, hyperthyroidism, gastrojejunostomy and other factors, or it may be caused by taking medication, and prompt medical attention is recommended. The normal range of fasting blood glucose is 3.9~6.1mmol/L, the normal range of blood glucose two hours after meal should be less than 7.8mmol/L, and the normal range of random blood glucose should be less than 11.1mmol/L. Therefore, no matter it is the fasting blood glucose, the two hours blood glucose after meal, or the random blood glucose, the 13.9mmol/L is higher than the normal range. Elevated blood glucose value may be caused by diabetes mellitus, but also by hyperthyroidism, after gastrojejunostomy and in a state of stress, such as trauma, acute infections, etc. In addition to this, long-term use of glucocorticosteroids, such as prednisone, etc., may also cause high blood glucose. It is recommended to go to the hospital and ask the doctor to make a judgment if there is an abnormal blood glucose value.