When I had ds the nurse explained to us that putting milk in th microwave was not good, however, she understood in real life you couldnt wait forever or it wasnt convenietn, so she thought it would be ok. The only reason its not adviced is for the hotspots but if you do dhake it really well and make sure its not too hot you should be ok. We never warmed his milk, but I have friends who have used it and they put it in for 15 deconds at a time and shake it really well and check it. Hope this helps, CHristie