The influence of renal threshold on the interpretation of urine tests for glucose in diabetic patients.

A knowledge of the renal threshold for glucose is important in the interpretation of urine tests in diabetes. We describe a simple method for determining renal threshold from blood and urine tests performed by the patients themselves. In a group of 65 insulin-dependent diabetic patients there was a wide variation in renal threshold, with a mean of 130 mg/dl (range 54-180 mg/dl). Threshold tended to rise with age, and it is suggested that the higher the renal threshold, the higher is the mean blood glucose achieved by the patient (r = 0.50, P = < 0.001). The change in blood glucose required to convert urine tests from 0% to 2% is very variable and ranged from 36 to 288 mg/dl (mean 110 mg/dl). The simple method that we describe may improve understanding of the significance of urine test results without the necessity for hospital admission.