How to Properly Freeze, Thaw & Store Breast Milk

March 13, 2020


We know it. You work hard to give your baby breast milk! So hard, in fact, that saving every drop of expressed milk is a priority for many moms. If you’re new to pumping and storing your milk, you may have a lot of questions about safely storing the breast milk you work so hard to provide for your little one. 

1 Natural Way is here to help you feed your baby and make sense of some of the confusing advice out there about proper breast milk storage. 

How to store breast milk safely

Storing your expressed breast milk is a great way to ensure your baby gets all the nutrients and benefits of milk, even when you’re not around. When pumping and storing your breast milk, make sure to always wash your hands, as well as any pump parts and storage containers that will come into contact with the milk.

Here’s an easy to reference chart, followed by some additional detail to help you quickly learn the dos and don’ts of storing breast milk.


Breast Milk Storage Reference Chart

Type of milk Storage place Storage temperature Safe storage time
Freshly expressed milk Room temperature 77℉ or colder 25℃ or colder Up to 4 hours
Freshly expressed milk Insulated cooler pack 59℉ * or colder 15℃ * or colder Up to 24 hours
Freshly expressed milk Refrigerator 40℉ or colder 4℃ or colder Up to 4 days
Freshly expressed milk Refrigerator freezer or Deep chest freezer 0℉ or colder -18℃ or colder Up to 6 months recommended; 12 months acceptable (deep freezer advised for over 6 months*)
Thawed frozen milk (unused) Refrigerator 40℉ or colder 4 ℃ or colder Up to 24 hours Do not refreeze
Thawed frozen milk (unused) Room Temperature 77℉ or colder 25℃ or colder Up to 24 hours Do not refreeze
Thawed frozen milk (partially consumed) Refrigerator 40℉ or colder 4 ℃ or colder Up to 24 hours Do not refreeze
Warmed milk (after thawing) Room Temperature or Refrigerator 77℉ or colder 25℃ or colder Up to 24 hours Do not refreeze

* Indicates temperature and storage recommendations from kellymom.com. All other temperatures, times and storage guidelines from the CDC.

Containers for breast milk storage

Store your breast milk in clean breast milk bottles or storage bags. Leave some room at the top, because the milk will expand when it freezes. Always write the date of expression on the bottle or bag.

Breast milk storage bags

Many moms like milk storage bags because they come sterile and don’t require any preparation. Additionally, frozen milk tends to thaw faster in bags than in bottles. While you can pump directly into some bags, many require moms to transfer expressed milk from a collection bottle to the bag for freezing – then back to a bottle for feeding.

Pro tip: Store breast milk bags flat so they defrost faster, and take up less room in the fridge or freezer.

Breast milk storage bottles

Breast milk storage bottles almost always double as milk collection bottles, allowing you to pump directly into them and then refrigerate or freeze them. A nipple can also be added at feeding time. This means less milk transfer from container to container (less hassle, mess and supplies to deal with). Bottles will need to be sanitized before each use, however, and take up more room in your refrigerator and freezer than storage bags.

Can you mix breast milk from different days or containers?

Mixing breast milk from different days is absolutely fine. But refrigerate freshly expressed milk before adding it to a container of previously expressed milk that has been in the fridge. When writing the date on the container, count from the day of the first expression.

How long does breast milk last in the fridge?

In clean conditions, freshly expressed breast milk can be safely stored at room temperature for 4 hours, in the fridge for up to 4 days, and in a deep freezer for up to 12 months.

When storing your milk, always choose the coldest place (like the back of the fridge or the bottom of the freezer – never on the door).

Many moms find it convenient to store breast milk in 3-5 oz. feeding portions. Since thawed milk cannot be refrozen, and partially consumed breast milk is only good for a couple of hours, this minimizes waste (and no mom likes to see her liquid gold go down the drain!).

How long is frozen breast milk good for?

According to the CDC, breast milk that is frozen at or below 0 degrees Fahrenheit (-18 degrees Celsius) can remain in the freezer for about 6 months (although up to 12 months is acceptable). The CDC acknowledges that freezing keeps food safe almost indefinitely, but recommends these storage limits to preserve the quality of the milk.

How to thaw breast milk from the freezer

Always thaw the oldest milk first – this is the key reason to write the date of expression on your storage bottle or bag. Thaw frozen milk in the fridge one day before you intend to use it or under lukewarm running water (or in a container of lukewarm water).

Never refreeze frozen milk that has been thawed. The build-up of bacteria makes it unsafe to consume.

Once thawed, breast milk is good for 24 hours in the fridge.

Pro tip: Thawed breast milk might look or smell different from freshly expressed milk. When frozen milk thaws, the creamier fat sits on top. You can gently swirl the bottle to mix it.

How long is thawed breast milk good for?

Once thawed in the refrigerator, frozen breast milk is good in the refrigerator for up to 24 hours. If the baby drinks some, you can safely keep the remainder for up to 2 hours, but after that it should be discarded.

Thawed breast milk that is brought up to room temperature should be used within 2 hours. The CDC does not recommend leaving breast milk out at room temperature to thaw.

Pro tip: Some babies don’t like to drink thawed breast milk because it can taste a little different from freshly expressed milk. If your baby falls into this camp, try scalding your breast milk prior to storing it in the fridge or freezer (scalding will help minimize the change in taste but can also reduce beneficial components).

How long does breast milk last after warming?

Once breast milk is warmed, it should be used within 2 hours.

You can warm breast milk from the fridge by running it under warm water or placing it in a warm water bath for a few minutes. Never microwave breast milk or put it in boiling water, as this can create hot spots that scald the baby.

Keep in mind that the milk doesn’t have to be warmed - some babies are content to drink it cold or lukewarm.

How will I know if breast milk is spoiled?

You’ll know if your breast milk is spoiled by the smell. While thawed breast milk can smell or look different from freshly expressed milk, it will smell sour or rancid if it’s gone bad.

1 Natural Way is committed to helping moms feed their babies. Whether you breastfeed and pump, or pump exclusively, knowing how to properly store and thaw breast milk will make your life easier.

1 Natural Way offers the best storage solutions from the most trusted brands and ships them to you for free! Still need your breast pump? Find out if you qualify for a no cost pump through insurance by filling out our easy form.

* Based on the Center for Disease Control (CDC) recommendations.

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