Reading your HbA1c — what the number means
A 3-month blood-sugar report card: the ranges, the conversion to average mg/dL, and the limits of A1c when glycemic variability is high.
HbA1c is your blood sugar report card for the last 3 months. It measures how much sugar has stuck to your red blood cells, whose lifespan is about 90 days.
The ranges that matter
- Below 5.7% — Normal
- 5.7% to 6.4% — Prediabetes
- 6.5%+ — Diabetes (two tests = diagnosis)
- Goal for most with diabetes: under 7%, individualised by your doctor
Translating to average blood sugar
Each 1% of HbA1c roughly corresponds to a 28-29 mg/dL change in average blood sugar. So HbA1c 7% ≈ average 154 mg/dL, 8% ≈ 183, 9% ≈ 212.
What HbA1c doesn't tell you
It does not show variability. Two people with HbA1c 7% can have very different lives — one steady at 154, the other swinging 60-250 daily. The second is much more dangerous. That's why your doctor may also want a CGM trace or a logbook.