Validity of urine glucose measurements for estimating plasma glucose concentration.

Both physicians and diabetic patients have traditionally relied on measurement of glycosuria as an indirect method of estimating plasma glucose concentration to guide adjustment of insulin and diet therapy. Our observations on the correlation between mean plasma glucose concentration with simultaneous urine glucose concentration or excretion rate re-emphasize the limitations of this approach. Although our observations show a significant correlation (P less than 0.0001) between plasma glucose concentration and urine glucose concentration or urine glucose excretion rate, the wide confidence limits [95% confidence limits (minimum) +/- 150 mg/dl] on plasma glucose concentration estimated from urine glucose measurements limit the clinical applicability of such estimates. Differences among subjects in the renal resorption of glucose contribute to the wide variance of estimates. However, significant variability in renal glucose resorption within individuals is documented, further reinforcing the limitations of urine glucose determinations for reliable estimates of plasma glucose concentrations. Diabetologists need to reconsider the applicability of urine glucose measurements in evaluation of adequacy of therapy and in adjustment of insulin dosage.