Patients with chronic renal failure are oliguric or anuric and sometimes polyuric. The following is a specific analysis of the causes of polyuria: 1. Patients with chronic renal failure with poor glycemic control, when blood glucose is high in the blood and urine sugar is also high, and urine sugar produces osmotic diuresis, polyuria will occur. 2. Patients with chronic renal failure are caused by damage to the renal tubules. In the process of urine production, first of all, most of the liquid in the blood and some small molecules including the waste in the body are precipitated under the action of the glomerulus, and then about 70% of the water is recycled when it flows through the renal tubules. Polyuria can occur at this time.3. The combined use of diuretics and other diuretics can also lead to polyuria.