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How to Store Breastmilk to Maximize Freshness

Updated: Aug 12, 2019

*The following guidelines apply for healthy, full-term babies. If your baby is preterm, seriously ill, and/or hospitalized, discuss milk storage guidelines with your baby’s doctor.

Before expressing and handling breastmilk, wash your hands and make sure all your pump parts and milk storage containers are clean. After you’ve expressed some milk,

  • Put the milk in a breastmilk storage bag or clean glass or BPA-free plastic container with a tight-fitting lid.

  • Label the container with the date and, if you will be giving the milk to a childcare provider, your baby’s name.

  • Store:

  • Freeze any milk you will not be using within 4 days right away.

  • Squeeze excess air out of the storage bag before sealing, and leave at least an inch of space at the top of the container so the milk has room to expand.

  • Place the container in the back of the refrigerator or freezer—away from the door and sides—where the temperature is the coolest.

  • Lay milk storage bags flat to freeze. Consider putting them inside another freezable container or ZIPLOCK® bag to prevent them from sticking to the freezer rack and touching other foods.

  • When you are ready to use your stored milk, use the oldest first. REMEMBER: First in, first out. (See our guidelines for thawing and feeding stored milk.)

Keep in mind the above guidelines are general ones. Factors such as temperature fluctuations in the refrigerator and freezer can affect the quality and safety of your milk. Like other types of milk, bad breastmilk smells and tastes sour. If this is ever the case with your stored milk, discard it. Also, be sure to use only bags designed for storing milk—not disposable bottle liners or other bags.

Milk Storage FAQ

How much milk should I store?

Start with 3 ounces per container and adjust as needed. Also consider storing some smaller portions—1 to 1.5 ounces—for when baby wants a little more or needs a small snack until you two are reunited for the next feeding.

Can I combine new milk with older milk?

Yes, you can add freshly expressed milk to refrigerated or frozen milk you pumped in an earlier session. However, cool the fresh milk in the refrigerator or in a cooler with ice packs first. Otherwise, the warm breastmilk could cause the frozen milk to partially thaw. Also, go by the date of the oldest pumped milk.

What do I do with milk I’ve pumped at work?

You can either store your milk in a refrigerator—including one that’s shared with coworkers—or in an insulated cooler bag with ice packs. Milk can be stored in a cooler for up to 24 hours. By that time, you can either use, refrigerate, or freeze your milk.

How can I monitor the temperature of my refrigerator and freezer?

The Centers for Disease Control and Prevention recommends using an inexpensive, freestanding appliance thermometer to determine your fridge’s and freezer’s temperatures. Having a thermometer can be especially important in case of a power outage.

What if the power goes out?!

Keep the refrigerator and freezer doors closed as much as possible. Unopened freezers keep milk and other foods safe for about 48 hours if full, and 24 hours if half full. An unopened refrigerator will keep food cold for about 4 hours.

Once the power comes back on, check on your milk. Frozen milk that has started to thaw but still contains ice crystals can be refrozen. Completely thawed but still cold milk can be transferred to the refrigerator and used within 24 hours.

As difficult as it may be, when it doubt, throw it out.

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