The purpose of this study was to determine the correlation between age and the percentage of total glycohemoglobin (%tGHb) and that of hemoglobin Alc (%HbA1c) in an adult population without known diabetes. The %tGHb was determined by a semi-automated gravity elution method and by an automated high-performance liquid chromatography (HPLC) method in 210 and 147 subjects without known diabetes, respectively. The %HbA1c, was determined by ion-exchange HPLC in 109 subjects without known diabetes. There was a modest age-related increase in %tGHb and %HbA1c. The mean increase was approximately 0.11% to 0.15% per decade depending on the analytic method used. However, the variance was very large. In conclusion, there is an age-related increase in %tGHb and %HbA1c. However, the increase is only modest and has only a minor effect on a determined reference range in adults.