You can leave it out for 5 hours at room temp or if you fridge it you don't have to warm it up. Like us baby's can drink cold stuff too. I mix my little guys oatmeal with Breastmilk and feed it to him straight from the fridge and he doesn't mind :)

originally I was going to do formula but here lately they would get so full they would bruise up and I could not get the milk to release so my SO (tmi I apologize) messaged my tatas till it released.so today he bought me a pump and I got 2oz out of each side @mrsmoore

yes it could cause constipation stick with what you pump ,to reheat put under warm water not hot, are you trying to up supply?