The present invention is drawn to a method of measuring glycated hemoglobin, which can comprise steps of establishing multiple age-specific groups of red blood cells, and measuring HbA1c levels of at least one of said groups. In another embodiment, a system for measuring glycated hemoglobin can comprise a separating device configured to separate red blood cells into multiple age-specific groups, and a measuring device configured to measure HbA1c levels of at least one of said groups.