"I was just wondering if I have expressed milk and refrigerated it and then warmed it how long can I keep it out before discarding it?"

Breastmilk has an antibacterial property which makes it safe to sit at room temperature for 6 - 10 hours. It can be stored in the refrigerator for 3 - 5 days and in a freezer for up to four months. It is important to label and date your milk so you use the oldest first.