The Influence of Renal Threshold on the Interpretation of Urine Tests for Glucose in Diabetic Patients

Abstract

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.

Tests of Glycemia in Diabetes

“…The above recommendations are supported by both clinical experience and extensive research investigations (2,(9)(10)(11)(12)(13)(14)(15)(16). Unfortunately, despite the welldocumented advantages of SMBG over urine glucose testing, most patients with diabetes still do not perform SMBG on a regular basis (17)(18)(19).…”

“…Specifically, patients should be taught that although urine glucose measurements correlate with blood glucose measurements, urine glucose testing provides only a rough estimate of prevailing blood glucose levels (2,(10)(11)(12)(13). Most importantly, patients should be taught that urine glucose testing provides no information about blood glucose levels below the renal threshold, which for many patients today is the target range for blood glucose (7).…”

Morning Spot Urine Glucose-to-Creatinine Ratios Predict Overnight Urinary Glucose Excretion in Patients With Type 2 Diabetes

“…Influential variables affecting UGE include the circulating glucose loading to the glomeruli, glomerular capacity to filter glucose into the renal tubule, and albuminuria [171819]. On the basis of previous studies [171819], we attempted to minimize the effects of glomerular filtration capacity by excluding participants who had less than 60 mL/min/1.73 m 2 of eGFR, and adjusted potential variables that may influence this analysis by adopting basal/stimulated glucose, HbA 1c , and GA as glucose load to glomeruli and staged albuminuria (normo-, micro-, and macroalbuminuria) classifications. As expected, the intra-class relationship between 8-hr UGCR and M-UGCR was significantly correlated in participants with T2DM (ICCs in NGT, pre-diabetes, and T2DM were 0.155, 0.049, and 0.943, respectively).…”

Tests of Glycemia in Diabetes

“…Specifically, patients should be taught that although urine glucose measurements correlate with blood glucose measurements, urine glucose testing provides only a rough estimate of prevailing blood glucose levels (3,(11)(12)(13)(14). Most important, patients should be taught that urine glucose testing provides no information about blood glucose levels below the renal threshold, which for many patients today is the target range for blood glucose (8).…”