Diabetic patients appear polyuria reasons mainly include the following: 1, high blood sugar will cause elevated urinary glucose, which produces osmotic diuretic effect, leading to polyuria; 2, diabetic patients because of polyuria will appear dry mouth, will increase the amount of water consumption, and after drinking will also increase the excretion of urine; 3, diabetes will damage the patient’s renal function, especially the renal tubules, which is responsible for concentrating the urine. When diabetes causes damage to the renal tubules, the urine cannot be effectively concentrated, which will also lead to an increase in urine output and polyuria; 4. Diabetic patients are at high risk for urinary tract infections, and once a urinary tract infection occurs, they will also experience urinary frequency and urgency, leading to an increase in urine output. Diabetic patients with polydipsia, polyuria, polyphagia, and weight loss as the typical three more and one less symptoms, if the patient has three more and one less symptoms, should be carried out as soon as possible for blood glucose monitoring. Currently, fasting blood glucose ≥7.0 mmol/L, or random blood glucose ≥11.1 mmol/L, or 2-hour blood glucose ≥11.1 mmol/L after the OGTT test are used clinically as the diagnostic criteria for diabetes. Recently, the indicator of glycated hemoglobin is also used as one of the diagnostic criteria for diabetes mellitus. Glycated hemoglobin reflects the average blood glucose level of the patient in the past 3 months, and diabetes mellitus can also be diagnosed if the glycated hemoglobin is ≥6.5%.