You are here
You can heat it up in the bottle itself. But no microwave as it can create hot spots. Place some boiling water in a cup and set the bottle (nipple off) in. Check regularly, shake and test on inner wrist for lukewarm.
have you looked at the bottles? it clearly says ready to use! no you don't have to heat them. think about this-when you had your baby in the hospital, there was probably no microwave in the room after they moved you out of labor and delivery. so i imagine that you did not heat it up then, so why do it now?