not sure what an A1C is but here they test your pee with a dip stick with markers on the side, depending what colours show up determines if you have diabetes and how bad it is.
underweight and craving sugary things like sweets could be your bodys way of telling you you need to eat more because sugar is turned not only into energy but stored as fat which you are lacking if you are underweight.
if you are eating too much sugary stuff you will be drinking more as you are getting more toxins go into your body and these need extra water to flush them out!
if you are craving chocolatey sweets you could be low in calcium. i crave chocolate occasionally which drives me potty as i am allergic to dairy! i have found that a cocoa and ricemilk 'hot chocolate' does stem the craving!