A1C of 5.7% is an average glucose of 117 mg/dL
Estimated average glucose at A1C 5.7%
117 mg/dL
- In mmol/L
- 6.5 mmol/L
- A1C entered
- 5.7%
- ADA range
- the range the ADA defines as prediabetes
An A1C of 5.7% corresponds to an estimated average glucose of 117 mg/dL, or 6.5 mmol/L, across roughly the previous two to three months. In IFCC units that A1C is about 39 mmol/mol.
The ADA calls 5.7% to 6.4% prediabetes. A value here is worth a conversation about repeat testing and about what your other numbers, particularly fasting glucose, are showing alongside it.
A1C 5.7% is the exact value at which the ADA prediabetes range begins, which makes it the most-searched figure on the whole scale. Sitting on the boundary is genuinely different from sitting well inside it: the ADA asks for a confirmatory test, and a result this close to the line is where that advice matters most.
Each additional tenth of a percentage point adds about 3 mg/dL to the estimated average, so 5.8% works out to roughly 120 mg/dL. That step is smaller than the 0.5-point tolerance NGSP allows on the assay, which is worth holding in mind before reading much into a one-tenth difference.
The look-back is weighted rather than even: the most recent weeks contribute more to the figure than the earliest ones, which is why an A1C moves before a full three months have passed.
A point-of-care fingerstick A1C and a venous laboratory draw can read differently on the same day. If two of your results disagree, the sample type is worth checking before anything else.
A sensible thing to ask at the next appointment is what this figure is expected to do, and when it will next be measured — which turns a number into something you can actually follow.
IFCC numbers look alarming to anyone used to percentages, because the scale is entirely different: a perfectly ordinary A1C reads as a two-digit figure in mmol/mol.
| A1C | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|
| 5.2% | 103 mg/dL | 5.7 mmol/L |
| 5.3% | 105 mg/dL | 5.8 mmol/L |
| 5.4% | 108 mg/dL | 6 mmol/L |
| 5.5% | 111 mg/dL | 6.2 mmol/L |
| 5.6% | 114 mg/dL | 6.3 mmol/L |
| 5.7% | 117 mg/dL | 6.5 mmol/L |
| 5.8% | 120 mg/dL | 6.7 mmol/L |
| 5.9% | 123 mg/dL | 6.8 mmol/L |
| 6.0% | 126 mg/dL | 7 mmol/L |
| 6.1% | 128 mg/dL | 7.1 mmol/L |
| 6.2% | 131 mg/dL | 7.3 mmol/L |
- Estimated average glucose (ADAG / Nathan) — eAG (mg/dL) = 28.7 x A1C - 46.7. Verified 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
How much average glucose is an A1C of 5.7%?
How is 5.7% classified?
Would a different lab report the same 5.7%?
Is 5.7% a target?
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