A1C of 10% is an average glucose of 240 mg/dL

Estimated average glucose at A1C 10%

240 mg/dL

In mmol/L: 13.3 mmol/L
A1C entered: 10.0%
ADA range: the range the ADA uses to diagnose diabetes

The estimated average glucose behind an A1C of 10.0% is 240 mg/dL, or 13.3 mmol/L. That A1C would appear as approximately 86 mmol/mol on a report using IFCC units.

This is inside the ADA diagnostic range. Higher values on this scale also tend to come with wider individual variation in what the corresponding average glucose actually is, so the estimate deserves proportionally less weight the further up you go.

Step up one tenth and the estimate moves by around 3 mg/dL: 10.1% gives about 243 mg/dL. Since a certified assay may itself vary by roughly 0.5 percentage points, a single tenth of movement between two tests is not really movement.

A steady day and a volatile day can average out to the same figure. If that distinction matters for you, it is continuous monitoring rather than a periodic average that shows it.

Anything that happened in the last fortnight is already influencing this figure, while something from four months ago has largely aged out of it.

Before reading much into this exact figure, note that NGSP certification allows a certified assay to differ from the reference method by about 0.5 percentage points. Two draws from the same person in the same week can land either side of a boundary without anything having changed.

If you are going to take one thing from this page, take the comparison rather than the reading: a number in isolation is trivia, and the same number tracked over time is information.

Convert a different A1C value

A1C to estimated average glucose, 9.5% to 10.5%
A1C	eAG (mg/dL)	eAG (mmol/L)
9.5%	226 mg/dL	12.5 mmol/L
9.6%	229 mg/dL	12.7 mmol/L
9.7%	232 mg/dL	12.9 mmol/L
9.8%	235 mg/dL	13 mmol/L
9.9%	237 mg/dL	13.2 mmol/L
10.0%	240 mg/dL	13.3 mmol/L
10.1%	243 mg/dL	13.5 mmol/L
10.2%	246 mg/dL	13.7 mmol/L
10.3%	249 mg/dL	13.8 mmol/L
10.4%	252 mg/dL	14 mmol/L
10.5%	255 mg/dL	14.2 mmol/L

Computed with eAG (mg/dL) = 28.7 x A1C - 46.7 (Nathan 2008). mmol/L is derived from mg/dL using the glucose factor 18.0182.

Estimated average glucose (ADAG / Nathan) — eAG (mg/dL) = 28.7 x A1C - 46.7. Verified 2026-07-30 against Nathan et al., Diabetes Care 2008 (ADAG study) (A population regression: in the ADAG study, individuals at the same A1C had meaningfully different mean glucose. The A1C assay itself carries about +/- 0.5 percentage points under NGSP certification.)

Official sources

Nathan DM et al., Translating the A1C Assay Into Estimated Average Glucose Values, Diabetes Care 2008 — The ADAG study that produced the eAG equation used on this page.
American Diabetes Association — Standards of Care in Diabetes — Where the A1C ranges quoted here are defined.
NGSP — A1C assay standardisation and certification criteria — Why two lab results half a point apart can mean nothing changed.

Frequently asked questions

What average blood sugar does an A1C of 10.0% mean?

The estimate is 240 mg/dL, equivalently 13.3 mmol/L, from the published ADA conversion for an A1C of 10.0%.

How does the ADA describe an A1C of 10.0%?

The ADA describes 10.0% as the range the ADA uses to diagnose diabetes. That is a definition of a numeric range rather than a diagnosis: the ADA asks clinicians to confirm results with a repeat test and to read them alongside your history.

Can something other than glucose produce an A1C of 10.0%?

Yes. Anaemia, recent blood loss, transfusion, pregnancy, chronic kidney disease and some haemoglobin variants all shift A1C independently of glucose, in either direction.

Does an A1C of 10.0% tell me about my glucose swings?

No. It is an average, and averages hide shape. Two people with this same A1C can have very different daily ranges; continuous monitoring is what shows that pattern.

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