Whether you’re exclusively breastfeeding or pumping milk to feed your little one (or any combination of the two), knowing how to safely store your breast milk is key to ensuring it stays fresh, nutritious, and safe.^1,2,3 This guide will walk you through the best ways to store, thaw, and warm your breast milk, so you can give your baby the healthiest start, whether you’re at home or on the go.

Why is Proper Storage Important?

Properly storing your breast milk helps make sure your baby gets all the nutrients they need while also preventing the growth of harmful bacteria.^1,2 Since breast milk is a living substance, it’s important to handle and store it correctly to keep it safe.

How to Store Your Breast Milk

Use the Right Containers

Breast milk should be stored in clean, airtight food-grade containers. You can use:^1,2

• Breast milk storage bags, which are made for freezing milk.
• Hard plastic or glass containers with tight-fitting lids.
• Baby bottles or breast milk storage containers, as long as they are sealed properly.
• Make sure whatever container you use is BPA-free (safe for your baby) and has been thoroughly cleaned before use.

Label Your Milk

Each time you pump, label your milk with the date it was expressed. This will help you keep track of how long your milk has been stored and ensure you use it within the proper time window.^1,2

Combining Your Milk

If you’ve pumped milk at different pumping sessions, it’s best to cool your fresh, warm milk prior to mixing it with milk that has already cooled in the refrigerator. Once your fresh milk has cooled, you can safely combine milk from multiple pumping sessions and freeze for later use.^1,2 

Freezing Your Milk

To save space and make storage easier, lay your breast milk storage bags flat to freeze. Just be sure to leave a small amount of “headspace” at the top of the bag, as the milk will expand as it freezes. This air gap can be removed once your milk is frozen.^1,2 

How Long Can You Keep Your Breast Milk?^1,2,3

Thawing Frozen Milk

When you need to use frozen milk, it’s best to thaw it in the refrigerator overnight or under cool running water. Never microwave frozen milk, as it can destroy some of the nutrients and create hot spots that could burn your baby.^1,2,3

Warming Milk

If you need to warm milk that’s been refrigerated or thawed, you can:^1,2,3

• Place the bottle or bag in a bowl of warm water for a few minutes.
• Use a bottle warmer
• You can also offer your baby cold milk straight out of the fridge – some babies don’t mind! 
• Make sure to always gently swirl and test the milk temperature on your wrist before feeding your baby to ensure it’s not too hot.

What Not to Do with Breast Milk

Here are a few important things to remember about handling breast milk:^1,2,3

• Do not refreeze milk once it has been thawed. Once thawed, it should be used within 24 hours and not refrozen.
• Do not add freshly pumped milk to milk that has already been stored (unless it has been cooled in the refrigerator first.)
• Do not leave milk out for more than 4 hours at room temperature, or longer than 4 days in the refrigerator.
• Never use a microwave to warm breast milk.

Is it Safe to Store Milk in Plastic Bags?

Yes, it is safe to store breast milk in plastic bags made specifically for this purpose. Just make sure the bags are BPA-free and made for freezer storage.^1,2 

Is it Safe to Store Milk in a Cooler Bag or Ice Chest?

What If I Have Questions?

If you are interested in learning more, these Aeroflow classes expand on some of the topics discussed above:

• Ultimate Breastfeeding Prep
• Lactation Q & A
• Moms Circle

Want More Info?

For a directory of Aeroflow’s other Care Guides offering information on pregnancy, baby care, and more, browse our comprehensive list of titles:

References