The A1c provides an insight on your past 2-3 month glucose
levels. Red blood
cells live on average 2-3 months. Excess glucose
rides on new red blood
cells, the A1c captures this and provides an estimated three month daily average.
" If a result such as 5.8% translates into an "average daily" value of 120 mg/dL, how can 5.8% be considered normal?"
An A1c of 5.8% equates to an eAG [estimated daily Average Glucose] of 120 mg/dl, key word is estimated.