Breast Milk Storage Guide: How to Store, Freeze, and Thaw Breast Milk

Safely storing your hard-earned breast milk shouldn't require remembering everything you learned in ninth-grade biology. Here's what you need to know to store, freeze, thaw, and use your pumped liquid gold with confidence—no textbooks required!

How to store breast milk

• Use storage bags specifically designed for breast milk (they’re thicker than food-storage bags and have a stand-up bottom) or glass/plastic food-grade storage containers with well-fitting lids.
• Date every container of breast milk. If you're sending milk to childcare, also label it with your baby's name.
  

How to freeze breast milk

• If you don’t plan to use your breast milk within four days of expressing it, freeze it.
• Freeze breast milk in small amounts—2 to 4 ounces—to avoid wasting any that your baby might not finish in a feeding.
• Leave an inch of space at the top of the container to accommodate expansion as the milk freezes. (Cough. Trust us on this one.)

• Don’t store breast milk in the door of either the fridge or the freezer as the temperature fluctuates every time the door is opened.

• Space-saving tip: If you’re using bags, place them flat in the freezer until they freeze, and then stand them up.

How to thaw breast milk

• Thaw your oldest breast milk first. The first containers you freeze should be the first ones you use, as the quality of breast milk can decline over time.
• Thaw breast milk overnight in the refrigerator, in a bowl of lukewarm water, or under lukewarm running water.
• Don’t use the microwave to thaw or heat breast milk because it can destroy nutrients in breast milk and create hot spots, which can burn a baby’s mouth.
• Breast milk can be served cold, at room temperature, or warmed—whatever your baby prefers.

Using frozen breast milk

• It’s normal for stored breast milk to separate—just gently swirl bottles to reintegrate the layers.
• Use breast milk within 24 hours of completely thawing it in the refrigerator (the clock starts once it's fully thawed—not when you move it from the freezer to the fridge).
• Use breast milk within two hours once it’s been brought to room temperature or warmed.
• You can add freshly expressed breast milk to refrigerated or frozen milk, but cool it down in the fridge before you do.
• Never refreeze breast milk once it's been thawed.
• Traveling? Freshly expressed milk can be stored in an insulated cooler with frozen ice packs for up to 24 hours before being transferred to a refrigerator or freezer.

Source: CDC’s Proper Storage and Preparation of Breast Milk