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A1c to Average Glucose Calculator

Convert A1c to average glucose.

How it is calculated

HbA1c reflects average blood sugar over roughly the last two to three months, as a percentage of haemoglobin that has glucose attached. The tool converts it to an estimated average glucose (eAG) with the linear formula eAG (mg/dL) = 28.7 × A1c − 46.7, where A1c is the percentage value from your lab report. The mg/dL value is rounded to a whole number. It also gives mmol/L using eAG / 18 (rounded to one decimal), the unit used in many countries. The formula is a population average. Your finger-stick readings can differ from it, since individual differences in red blood cell lifespan change the link. It cannot diagnose or manage diabetes; follow your doctor's targets.

Worked example

A lab reports an A1c of 7%. Multiply: 28.7 × 7 = 200.9. Subtract 46.7: 200.9 − 46.7 = 154.2, which the tool shows as 154 mg/dL. To get mmol/L, divide 154.2 by 18 = 8.567, shown as 8.6 mmol/L. In practice this means an A1c of 7% corresponds to average readings near 154 mg/dL, though single readings through the day will be both higher and lower.

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Common mistakes

  • Entering the A1c in mmol/mol (for example 53) when the formula expects the percentage (7.0).
  • Confusing eAG with a fasting glucose reading; eAG is an average over months, including after meals.
  • Expecting the result to match a home meter exactly; individual differences mean the estimate can be off.
  • Mixing up mg/dL and mmol/L when comparing with a target from another country.
  • Using the result after a recent blood transfusion, anaemia or similar conditions, where A1c itself is less reliable.

Sources

About this calculator

This calculator converts an HbA1c percentage into estimated average glucose (eAG) using the ADAG study formula (eAG in mg/dL = 28.7 × A1c − 46.7), the same equation many lab reports use to translate a three-month glycemic average into the mg/dL or mmol/L numbers patients see on a daily glucose meter.

Nurses, lab technicians, and diabetes educators use it to explain lab results in familiar units, and nursing and medical students use it to check A1c-to-glucose conversions while studying. It gives an estimate only — actual daily readings can vary from the calculated average.

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Comments (1)

  • Editorial team

    Many labs outside the US report A1c in mmol/mol, while this tool expects the percentage. To convert, multiply the mmol/mol figure by 0.0915 and add 2.15, so 53 mmol/mol is 7.0 percent. Enter that percentage, then read the glucose figures as a rough long-term average, not a daily target. Your doctor sets the targets. Which unit does your lab report use?

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