An A1C (HbA1c) test gives you a picture of your average blood glucose control for the past 2 to 3 months. The results give you a good idea of how well your average suger level instead just a one time blood glucose level (most of time, doctor will ask you to do fasting plasma glucose test), but result only show you that day ur body how to produce and process insulin to counteract the rise in glucose levels, but not avarage and even after ur eating.
Normal Doctor won't give u a A1C test if u don't ask him when u have annual check up, because cost more.