Well I'm not sure what others will say. I know some book I read said not to microwave because it could scauld them. However, my LO is 1 year and 1 month old and I have been microwaving her bottles for as long as I can remember. Currently, she drinks her milk from a sippy cup "which I have to hold" and I put that in for 20 seconds to take the chill off. When she was drinking 8 oz bottles, I would have to put it on 30 to warm it up.