What it measures: Average blood sugar over the past 3 months.
Normal Range:
- Below 5.7% = Normal
- 5.7–6.4% = Prediabetes
- 6.5% or higher = Diabetes
Why it’s done: To diagnose and monitor diabetes.
Interpretation: Higher levels suggest poor glucose control.
Source: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)