Fasting for too long may not raise blood glucose significantly, but the body regulates itself to keep blood glucose stable. When fasting for too long, the body does not have enough energy to replenish itself, and the body replenishes its blood glucose level through gluconeogenesis to ensure the normal conduct of life activities. The body can regulate itself to keep the blood glucose level stable, but generally there will not be a significant increase in blood glucose. Glucose is the main source of energy in the body and plays a very important role in the normal conduct of life activities. Food is an important source of glucose replenishment, but the body will also have a reserve of blood glucose, short-term glucose deficiency will have the liver to replenish, persistent energy deficiency the body will replenish glucose through gluconeogenesis to avoid severe hypoglycemia. Fasting too long to pay attention to replenish energy, if necessary, monitor changes in blood glucose, such as abnormalities in blood glucose, should be promptly to the hospital, under the guidance of the physician to give treatment.