The typical symptoms of diabetes mellitus are three polyuria and one less, namely polyuria, polyphagia, polyphagia and weight loss (wasting). The causes of polyuria caused by diabetes mellitus: 1, diabetes mellitus patients with increased blood sugar, too much sugar can not enter the cells to use, can only be excreted from the urine, glucose in the urine leads to an increase in osmotic pressure, the renal tubular reabsorption of water to reduce polyuria. 2, diabetes mellitus patients are prone to thirst, increased water consumption will appear polyuria, nocturnal urination, the volume of urine per day and night can reach 3000ml-4000ml, up to 10,000ml or more. In conclusion, polyuria in diabetes is one of the typical symptoms of diabetes mellitus, so actively control blood sugar and reduce polyuria after blood sugar reaches the standard.