Storing Breast Milk: Everything Parents Need to Know

Producing more breast milk than your baby needs is a great problem to have. In my experience as a physician, most breastfeeding parents worry about producing too little milk, especially when they start pumping in addition to nursing. That's why you've more than likely received the advice to never throw out your breast milk, but freeze it instead.

According to the Centers for Disease Control and Prevention, freshly expressed breast milk can be only safely stored in the refrigerator at 40 degrees F (4 degrees C) for 4 days. However, fresh breast milk can also be stored in the freezer at 0 degrees F (-18 degrees C) or colder safely for 6 to 12 months.

Learn more about how to freeze and unfreeze breast milk safely.

How to Freeze Breast Milk

After pumping, immediately pour the milk into breast milk storage bags or clean food-grade containers with tight fitting lids made of glass or plastic. Leave an inch at the top of the container because milk expands when it freezes. Also, it's a good idea to store your breast milk in smaller portions (2 to 4 ounces in a bottle/bag) so it will freeze and thaw faster.

Label every storage container with the date of breast milk collection. If you will be delivering breast milk to a childcare provider, clearly label the container with the child’s name. Talk to your childcare provider about other requirements they might have for labeling and storing breast milk.

Place the bottles/bags in the freezer immediately. Store the milk in the back of the freezer (not in the door), where it's the coldest, and don't remove it until you're ready to thaw it and serve it to your baby.

Use the oldest milk first or discard it if you won't be using it safely in the future. If you've got plenty already in your freezer and you're still able to pump and store more, don't feel bad about discarding the oldest milk in your freezer. Either way, if it's too old, it's best to throw it away.

Additionally, breast milk can be stored in an insulated cooler bag with frozen ice packs for up to 24 hours when you are traveling. Once you arrive at your destination, milk should be used right away, stored in the refrigerator, or frozen.

How to Thaw Breast Milk

There are a few ways to thaw frozen breast milk. If you don't need the milk right away, simply move it to the refrigerator, where it will take 24 hours to thaw. Warm the milk by running warm water over the bag or bottle of milk and use it within the next 24 hours.

If you need it immediately, remove it from the freezer and run warm water over it until it's at room temperature.

Once you've thawed breast milk, don't refreeze it. Also, do not thaw or heat it in the microwave. You run the risk of overheating the milk, which can harm your baby and destroy the milk's enzymes and immune properties.