Your A1C (also called HbA1c) is a lab test that shows the percentage of your red blood cells' hemoglobin that has glucose attached to it. Because red blood cells live for roughly three months, A1C reflects your average blood sugar over the past two to three months rather than any single moment.
Estimated average glucose (eAG) translates that percentage into the same units you see on a meter or CGM — mg/dL (common in the US) or mmol/L (used in Canada and most other countries). The conversion comes from the A1C-Derived Average Glucose (ADAG) study, which compared A1C results with months of frequent glucose readings: eAG (mg/dL) = 28.7 × A1C − 46.7, and dividing by 18 (more precisely 18.016) converts mg/dL to mmol/L. An A1C of 7%, for example, works out to about 154 mg/dL or 8.6 mmol/L.
Your eAG may not match the average on your own meter. Fingerstick checks are often taken at particular times (before meals, first thing in the morning) and miss highs and lows in between, and things like anemia, recent blood loss, pregnancy or kidney disease can change how A1C relates to real glucose levels. eAG is an estimate for the average person in the study, not an exact reading for you.
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A1C ↔ eAG converter
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6.5% or higher is in the diabetes range. 7% or below is a common treatment target for many adults (ADA) — your own target may differ.
Formula: eAG (mg/dL) = 28.7 × A1C − 46.7 · eAG (mmol/L) = eAG (mg/dL) ÷ 18.016
Medical Disclaimer: This content is informational only and is not medical advice. Always consult your doctor or a qualified healthcare professional before making changes to your diabetes management plan. If you think you are having a medical emergency, call 911.
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