I Am 64 Y. O. And Never Had A Problem.

I am 64 y. o. and never had a problem. Yesterday, with a blood draw, they found my a1c to be 11.2. Is it possible that diabetes comes on that quick? I know my diet is full of carbs but I'm not overweight, don't drink much, and almost totally avoid sodas. My question is, should I be in panic mode, and to what extent should I hope that diet modification will help get me under control?