RP from April 2012: How long is warmed BM good for?

Luvmy2sons

I have to take LO one out today, and I have a bottle of BM I pumped last night and put into the fridge. I'm not sure if there's somewhere to warm it when out, so can I warm it before I go? How long is it good for? Or should I just take it cold and hope there's somewhere I can get a cup of hot water to warm it in? I used to have a travel bottle warmer for my younger kids, but I use drop-ins bottles, so they either took forever to warm up, or never warmed at all.