The excessive drinking in diabetic patients is caused by polyuria. The reason why diabetic patients urinate more is that when the patient’s blood sugar is very high, such as fasting blood sugar greater than 11 mmol/L, the patient’s pancreatic islet function is very poor, insulin secretion is very little, and the glucose in the blood cannot be used by the organism and can only be circulated in the blood. The glomerulus of the kidney can completely filter the glucose in the blood into the urine, and too much glucose in the urine will produce an osmotic diuretic effect and make the patient urinate more. Patients appear polyuria, polyuria inevitably leads to a decrease in blood volume, the body in order to maintain blood volume, the thirst center activates, the patient will appear irritable thirsty and drink more, will replenish water, diabetic patients are due to high blood sugar leading to polyuria and then caused by the polyuria.