You can thaw your frozen breastmilk by holding it under cool running water. Gradually increase the water temperature to heat it to a comfortable feeding temperature. This is a temperature that feels warm, not hot, on your wrist. Periodically mix the milk in the bag or bottle by swirling gently, as it defrosts. Milk can also be thawed in a refrigerator overnight. Do not thaw or heat your milk in a microwave or directly on the stove.