Polyuria is defined as a 24-hour urine output of more than 2500ml. Under normal circumstances, the 24-hour urine volume is 1000-2000 ml, and greater than 2500 ml is polyuria. It may be caused by physiological reasons such as drinking a lot of water and applying diuretics. It may also be caused by uremia, diabetes and other pathologic causes. 1. Physiological reasons: when drinking a lot of water, the blood is diluted, blood volume increases, glomerular filtration rate increases, tubular reabsorption decreases, so the urine volume will increase, or when using diuretics, the urine volume will also increase a lot. If normal water intake or after stopping the drug, the urine volume returns to normal, at this time do not consider the emergence of renal disease, belong to physiological polyuria. 2. Pathological causes: such as dysuria is divided into central dysuria and renal dysuria. Central dysuria is caused by various reasons of insufficient secretion of antidiuretic hormone. Renal dysuria is caused by insensitivity of the distal tubules and collecting ducts to antidiuretic hormone due to renal disease. In diabetes mellitus, glucose in the urine leads to an increase in the osmotic pressure of the urine, which produces osmotic diuresis and ultimately leads to an increase in urine output. If the patient occurs polyuria, it is recommended to go to the regular hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.