HbA1c estimates your average blood glucose over roughly the previous 8-12 weeks. An HbA1c of
6.5% or above meets the laboratory threshold used to diagnose diabetes. Your result is
slightly above that threshold.
ADA diagnostic standards
HbA1c can be misleading in some situations, including anemia, recent blood loss or transfusion, kidney disease, and certain hemoglobin disorders, because these change red-cell lifespan. Tietz Textbook of Laboratory Medicine, 7th Edition explains that HbA1c generally reflects glycemia over the preceding 8-12 weeks.
For many adults with diabetes, an HbA1c target below 7% is often used, but targets should be individualized, particularly at age 63. Your value of 6.6% is close to this usual treatment target, so early action may allow control with lifestyle measures, with or without medication depending on the confirmatory tests and risk profile.