The causes of high fasting blood glucose in diabetes mellitus include irregular use of medication, dawn response, Sumuje phenomenon, and eating too much for dinner. 1. Unstandardized medication: If diabetic patients take insulin or oral hypoglycemic drugs and do not standardize the use of fasting blood glucose can not be effectively controlled, resulting in high fasting blood glucose. 2. Dawn response: Dawn phenomenon usually occurs in the early morning. At this time, such as adrenaline, glucocorticoids and other blood sugar-raising hormone secretion increases, these hormones have blood sugar-raising effect, so gradually fasting blood sugar is high. 3. Sumuje reaction: Hypoglycemia usually occurs at night in diabetic patients. Because of the occurrence of hypoglycemia, the body will respond to the hypoglycemia and adjust to raise blood sugar, thus appearing fasting blood sugar is high. 4. Eating too much dinner: such as diabetic patients at night to eat late-night snacks bad habits. If there is such a bad habit as eating too much dinner, it will lead to high fasting blood sugar. Diabetic patients should be strict diabetic diet, regular medication, regular monitoring of blood glucose. Diabetes high fasting blood sugar may have other reasons, such as high fasting blood sugar for a long time, should consult the hospital in time, under the guidance of the doctor for treatment, do not blindly use drugs to delay the condition.