The classic symptoms of diabetes mellitus are polydipsia, polyuria, polyphagia, weight loss, polydipsia is due to glucose can not be utilized, with the urinary discharge to produce hyperosmolar diuresis, the patient's urine volume and the number of times of urine have increased, the body discharges too much water leading to the patient's thirst is obvious, the glucose can not be utilized, lack of energy in the body leading to the patient's hunger is clear, due to the disorder of glucose metabolism leading to the disruption of protein metabolism, the emergence of a negative nitrogen balance leading to the Patients wasting obviously, this is a typical diabetes three more than one symptom. Diabetes mellitus can also have many acute and chronic complications, some patients are not with three more and one less as the first symptom, but with repeated skin infections, such as boils, carbuncles and diabetic ketoacidosis as the first symptom, so when the above symptoms occur, you should pay attention to checking the blood glucose to see if diabetes mellitus occurs, and give timely treatment.