How can I lower my hemoglobin A1c levels?

Improve blood sugar. The way to improve your hga1c is to improve your average blood sugar. Work to keep your fasting blood sugars near normal and watch your diet carefully so that the rise in blood sugar after a meal is not too high.
Hgb A1c is a marker. Of steady state blood glucose, and is formed spontaneously by nucleophilic attack of the b-globin n-terminal amino group on the anomeric carbon (aldehyde carbon) of glucose. Following a chemical rearrangement (an amadori rearrangement), the modification on hemoglobin is "locked in". The best way to lower is to control your blood sugar consistently through time. It will fall as rbcs turnover.