Ideally, bottles of formula should be made fresh for every feeding to minimize the risk of bacteria growth. It is possible to make bottles up to 24 hours in advance and store them in the refrigerator for added convenience. Bottles of formula or breast milk can be served cold, but some babies prefer warm liquids. Heat the breast milk or formula prior to feeding by using warm water.
Run the bottle under hot tap water to defrost frozen breast milk or to warm refrigerated milk.
Fill a bowl or pan with hot or warm water and put the bottle in it for a few minutes.
Invest in a bottle warmer for your kitchen or vehicle to heat your baby's bottles no matter where you go.
Squirt a few drops from the bottle onto your wrist to test the temperature of the milk or formula. It should be lukewarm to the touch and, if it is too hot for your skin, it is definitely too hot for your baby to drink.