The effects of chronic renal failure and hemodialysis on the glucose turnover rate, glucose carbon recycling, and glucose oxidation were evaluated in eight chronically uremic subjects. Six normal subjects served as controls. The studies were repeated in seven uremic subjects after they had been established on hemodialysis for 3 to 18 months. Glucose 13C(microliters) was administered by a prime-constant-rate infusion, and the isotopic enrichment of the whole glucose molecule (m + 6), ie, all six carbon atoms of glucose labeled with 13C and that of the C1 atom of glucose in the plasma were measured by mass spectrometry. It was assumed that the C1 atom of the glucose molecule represented the 13C enrichment of the individual glucose carbons. The "true" rate of glucose production was estimated from the dilution of the glucose 13C (microliters) mass (m + 6) in the plasma. In contrast to the whole glucose molecule (m + 6), recycling of tracer carbon resulted in an increased 13C enrichment of the C1 atom of the glucose molecule and an underestimation of glucose turnover ("apparent"). Glucose carbon recycling was estimated from the difference between the "true" and "apparent" rates of glucose turnover. The contribution of glucose to respiratory CO2 was quantified by comparing the 13C enrichment of expired CO2 with that of the plasma glucose carbon. The plasma glucose concentration after an overnight fast was similar in the uremic and control subjects (72.3 +/- 9.5 and 79.0 +/- 9.5 mg/dL, respectively; mean +/- SD).2+ while the "true" rates of glucose production were similar in both groups (normal: 2.02 +/- 0.19 mg/kg X min; uremic: 2.19 +/- 0.53 mg/kg X min).(ABSTRACT TRUNCATED AT 250 WORDS)