A1C of 5.5% is an average glucose of 111 mg/dL
Estimated average glucose at A1C 5.5%
111 mg/dL
- In mmol/L
- 6.2 mmol/L
- A1C entered
- 5.5%
- ADA range
- below the range the ADA defines as prediabetes
5.5% translates to an average glucose of about 111 mg/dL, which is 6.2 mmol/L in the units used across the UK, Australia and Canada. The IFCC equivalent of the A1C itself is close to 37 mmol/mol.
The ADA places this figure below the range it defines as prediabetes, which starts at 5.7%. That is a statement about where a number sits on a scale, not a verdict about your health, and it says nothing about which direction the number has been moving.
A1C 5.5% sits two tenths below the ADA prediabetes threshold, which is why it generates so much searching. The honest reading is that a single value this close to a cut-point tells you where you are on the scale and not which way you are heading; that takes a second test.
One tenth higher, at 5.6%, the estimate reaches about 114 mg/dL — a difference of roughly 3 mg/dL. Set against the 0.5 percentage points a certified assay may vary by, that is a very small step indeed.
The genuinely useful question is not what this single value means but how it compares with your previous one, and whether that difference is bigger than the measurement tolerance.
The mmol/L figure on this page is the mg/dL figure divided by 18.0182, the molar factor for glucose, so the two are consistent with each other rather than each coming from a different equation.
How readily an individual glycates varies, which is one reason a continuous-monitor average and a laboratory A1C often disagree in the same person even when both are measured properly.
Time spent in range and time spent high or low are separate questions from the average, and they matter clinically in ways an average cannot capture.
| A1C | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|
| 5.0% | 97 mg/dL | 5.4 mmol/L |
| 5.1% | 100 mg/dL | 5.5 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 |
- 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
What average blood sugar does an A1C of 5.5% mean?
What does the ADA say about 5.5%?
Does an A1C of 5.5% tell me about my glucose swings?
Can something other than glucose produce an A1C of 5.5%?
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