High blood glucose in the morning but normal in the afternoon is considered to be caused by dietary factors, or it may be caused by factors such as the Sumuje phenomenon and the Dawn phenomenon. 1. Dietary factors: If the food consumed in the morning has a high glycemic index and the food consumed in the afternoon has a low glycemic index, the situation of high blood sugar in the morning but normal in the afternoon may occur. 2. Sumuje phenomenon: diabetic patients with impaired glucose regulation may cause hypoglycemia at night, resulting in a rebound increase in blood glucose in the early morning causing an increase in fasting blood glucose, appearing in the morning high blood glucose in the afternoon normal. 3. Dawn phenomenon: blood sugar control is stable at night, no hypoglycemia has occurred, but early in the morning due to the imbalance of various hormone secretion leads to early morning fasting blood sugar rise, resulting in high blood sugar in the morning and normal in the afternoon. In the case of high blood glucose in the morning but normal in the afternoon, it is recommended to go to the hospital after excluding dietary factors.