The sugar in the blood is called blood sugar, and in most cases it is glucose. Most of the energy required for the activities of various tissues and cells in the body comes from glucose, so blood sugar must be maintained at a certain level to maintain the needs of various organs and tissues in the body. The fasting blood sugar concentration of a normal person in the morning is 80-120 mg%. A fasting blood sugar concentration exceeding 130 mg% is called hyperglycemia. If the blood sugar concentration exceeds 160-180 mg%, some glucose will be excreted in the urine, which is diabetes. A blood sugar concentration below 70 mg% is called hypoglycemia.