HbA1c reports your three month glucose story as a percentage, which confuses almost everyone at first. This converter translates it into estimated average glucose, the same mg/dL units your meter shows every day.
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Scientific references
Two languages for the same story
A glucose meter speaks in milligrams per deciliter, the number flashing back at you seconds after a fingerstick. The lab speaks in HbA1c percentage, the share of your hemoglobin that has picked up sugar permanently during the red blood cell’s life. Both describe average glycemia, yet the different units leave many people unable to connect the meter reading at breakfast with the lab result at the checkup. The ADAG study solved the translation problem by pairing continuous glucose monitoring with A1c in hundreds of people and fitting the line between them.
The arithmetic behind it
The relationship turned out to be strikingly linear. Multiply A1c by 28.7 and subtract 46.7 to get average glucose in mg/dL. An A1c of 7 percent maps to about 154 mg/dL, a number familiar to anyone who has compared lab results with meter averages. The fit is good across a wide range, which is why the formula now prints on many lab reports automatically as estimated average glucose.
Where the translation wobbles
Anything that shortens red blood cell lifespan lowers A1c without lowering true glucose, including hemolytic anemias, recent blood loss, and some hemoglobin variants. Pregnancy accelerates red cell turnover and skews results the same way. In these situations the meter average and fructosamine testing tell the story more honestly than A1c.
Using the pair together
The most useful habit is computing your own eAG after every lab draw and comparing it against your meter’s thirty day average. Persistent gaps between the two reveal timing blind spots, usually overnight or post meal spikes the meter schedule misses. That comparison, not the number alone, is where this conversion earns its keep.