No, you cannot lower your A1C overnight. The A1C test measures your average blood sugar levels over the past 2-3 months, so it takes time to see significant changes. However, you can take steps to improve your blood sugar levels immediately, which will eventually lower your A1C.
If your A1C is consistently high or you're struggling to manage your blood sugar, consult your doctor. They can adjust your treatment plan and provide personalized advice.