The dawn phenomenon and the somogyi effect are two situations in which high morning fasting blood glucose exists. 1. Dawn phenomenon: high fasting blood glucose in the morning, multiple blood glucose measurements at night, blood glucose control is still good, and no hypoglycemia occurs. It is mostly caused by the increase of blood glucose-raising hormones such as cortisol and growth hormone in the morning. Dawn phenomenon is one of the weak links in blood glucose management of diabetic patients, timely and accurate monitoring of blood glucose. 2. Somogyi effect: multiple blood glucose measurements at night reveal hypoglycemia, and fasting blood glucose is high in the morning. Generally, it is the rebound hyperglycemia caused by the increase of glucagon in the body due to hypoglycemia. The amount of insulin used before bedtime should be reduced appropriately. If you find that your fasting blood sugar is high in the morning, we suggest that you consult a doctor in a timely manner to clarify the cause and target treatment under the doctor’s guidance.