Safe storage of pumped milk

Breast milk frozen in storage bags

The proper handling and storage of pumped breastmilk is key to maintain its safety and nutritional qualities. Here’s how:


You’ll need either glass or BPA-free plastic bottles or milk storage bags before you begin pumping. (Breastmilk should not be stored in bottle liners or regular plastic bags.) Fun fact: breastmilk storage containers qualify as tax-deductible breastfeeding equipment.

Most mothers store milk in 2-5 ounce portions. If you know about how much milk your baby typically takes at a feeding, storing the milk in those portions can help reduce waste.


Freshly expressed breastmilk is safe at room temperature (up to 77 degrees F) for up to 6 hours, but leaving milk at room temperature for only 3-4 hours is best. In a warmer room (80-90 degrees F) milk should be used or refrigerated within 3-4 hours.

If you don’t plan to use your pumped milk within 4 hours, it can be chilled immediately in a fridge, freezer or cooler. Breastmilk can remain in the fridge (39 degrees F or cooler) for up to 3 days (after this the milk starts to lose antibodies) and can remain in the freezer (0 degrees F or cooler) for up to 6 months. If you have a deep freezer (-4 degrees F or cooler) you can store milk for up to 12 months. When freezing milk, keep in mind that the milk will expand slightly when frozen so you’ll need to leave some extra room in the storage container.

And it’s always best to keep milk in the back of the fridge or freezer where it’s coldest.


When you’re ready to use breastmilk from the freezer, it can be thawed in its container in the refrigerator overnight (which typically takes about 12 hours) or by placing the container directly into a larger container of warm water or under warm running water. Do not leave breastmilk out in room temperature to thaw. Remember to thaw and use the oldest milk first!

Do not use the microwave to thaw breastmilk, as it can damage the milk and heat unevenly creating hotspots that could burn your baby.

Thawed milk is safe in the refrigerator for 24 hours, and once the milk is warmed it’s best if used within 1-2 hours.

Keep in mind that milk does not HAVE to be warmed. If your baby accepts or prefers cold breastmilk it is perfectly safe to give it chilled.


After pumping it is safe to mix milks that are the same temperature (warm with warm and chilled with chilled). If the milk you are mixing is from different days, label your final storage container with the oldest date.

What to Do

Wash your hands

Before pumping or handling breastmilk, be sure to wash your hands with soap and water or clean your hands with hand sanitizer if you don’t have a nearby sink.

Label breast milk storage containers

Write the date, the volume of milk and (if traveling to a child care provider) your child’s name on every container.

If you did not pump directly into the container you intend to store the milk, carefully transfer it to the appropriate place and then label.

Swirl your milk, but do not shake

Oftentimes, the fatty portion of the milk will separate and settle at the top of the container. To mix everything back together, gently swirl the container. Avoid shaking the milk as this can damage proteins and other beneficial properties.

Get in the habit of chilling your milk right after it’s expressed

Unless you are giving the milk to your baby in the next 3-4 hours, immediately place the milk in a cooler pack, fridge or freezer.

If you know you will not need the milk you just pumped in the next 3 days, go ahead and freeze it (or you can always transfer from the fridge to the freezer after 3 days).

Check the temperature of warmed milk

To warm a bottle, place it in a container of warm water or under warm running water. Milk should never be microwaved. Always remember to check the temperature (by putting a few drops on your wrist) before offering it to your baby.


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