My husband is a beekeeper and we have hundreds of lbs. of honey in the basement. I agree w/ vioburn. You can use the microwave but it does destroy some of the nutritional properties of raw honey and it will melt/distort the bottle. However, if the honey is from a commercial distributer (you got it in the grocery store), is has more than likely already been heated so reheating it in the microwave isn't a big deal. Don't put it in for long (10 seconds at a time).
Honey doesn't go bad and all honey crystallizes at some point. Honey should be stored in a cabinet not in the refrigerator because it speeds up crystallization.