Everything You Need to Know: How to Store Your Breast Milk

Safety first, mama.

To all the moms that are heading back to work, want to ramp up inclusion of their partner in the feeding process or having a night-out for the first time (yes!), pumping and storing breast milk is the perfect way to ensure that your baby will be fed and you can enjoy your time away.

Keep reading to find out how storing breast milk can benefit both you and your baby.

Milk Storage Tips

Tips for Milk Storage & Safety

“Fresh milk straight from the source offers the most nutritional value and protective, immune-boosting properties, but we know that it’s not always possible to breastfeed on-demand,” says Wendy Wright, International Board Certified Lactation Consultant (IBCLC). To make things easy for you we’ve outlined a few of the best ways to keep your milk safe.

Safety Guidelines for Breast Milk Storage

  1. Room Temperature - Storage time (4hrs): Breast milk should ideally be put in a cool environment immediately or fed to your baby, but as long as it stays in a room cooler than 77°F it should maintain its freshness. This method is often useful for moms pumping in the middle of the night or just before heading home from work. Do not pour excess room temperature milk into already cooled or frozen milk containers. Cool the room temperature milk first if you wish to combine it with milk already in the fridge.

  2. Cooler Bag - Storage time (< 24 hours): Storing breast milk in a cooler bag is perfect for traveling or days away from home when you need to bring your milk and baby on the go. Breast milk coolers vary in shapes and some varieties include built-in cooling mechanisms. Any unused milk that remains in the cooler after 24 hours should not be fed to your baby, so this method is great for short periods of time, like day-trips.

  3. Refrigerator - Storage time (< 4 days): Breast milk stored in the fridge is best used within the following 3-5 days. After 4 days the milk starts to lose its anti-infection properties.

  4. Freezer - Storage time (< 6 months): Storing breast milk in the freezer is best if you don’t plan on using the breast milk within the next 4 days. This is a great method if you produce a lot of milk and want to have a back-up supply for days when you aren’t at home. It is best to use frozen milk within the first 6 months, but the milk stays good for up to 12 months.

  5. Previously Thawed - Storage time (< 12 hours in fridge): Previously thawed breast milk can stay in the fridge for up to 12 hours. Frozen milk should be thawed in the refrigerator. Keep in mind that thawed breast milk should ideally be used within the first 24 hours if kept in the fridge, but within 1-2 hours when thawed at room temperature.

Storage Guidelines for Freshly Expressed Breast Milk

When you store breast milk in the freezer it can stay good for up to 12 months. Keep in mind that the longer breast milk stays in the freezer, it will begin to lose its nutritional properties.

There are methods for storing breast milk in the freezer to ensure that your milk stays fresh. To avoid contamination, make sure that you are using BPA-free storage containers that are designed for storing breast milk. Be sure that your containers have a tight seal, and wash your hands before storing them.

The way you stack and organize your breast milk containers can also affect the milk's longevity in the freezer. Labeling each container with its storage date helps to keep track of how long your milk has been in the freezer. Always place your containers in the back of the freezer where it is coolest. If you use breast milk storage bags, you can stack them flat on top of each other to maximize space in your freezer. Glass containers are often recommended for deep freezing because they are more durable. Bags are great for shorter periods of time but are more susceptible to leaks.

How to Store Breast Milk in the Freezer

For the best storage solution in the freezer, divide your containers into the amount that your baby eats per feeding. This is typically around 2-4 ounces per container. Storing in smaller amounts will ensure that you don’t have any leftovers after thawing. Frozen milk is safest when thawed in the fridge. Remember that previously thawed, leftover milk can last in the fridge for up to 12 hours, but it can’t be refrozen. Refreezing breast milk can increase the risk of bacteria growth and breakdown of the milk’s nutritional properties.

How to Store Breast Milk In The Refrigerator

If you plan to store breast milk in the refrigerator, remember that it is best to store it immediately after expressing to maintain its freshness. You should store breast milk in the normal feeding amounts that your baby eats. If you have a large milk supply, you can freeze half of your containers and keep a few in the fridge that you know you will use during the week.

Here are some other rules of thumb when storing breast milk in the refrigerator:


  • Label containers with dates, store in small feeding amounts
  • Store breast milk immediately after expressing. (Remember it can last up to four hours at room temperature before cooling, but this will not maximize its fridge lifetime)
  • Store breast milk in the back of fridge
  • Move breast milk from fridge to freezer within the first five days if you don’t plan on using it


  • Store large, bulk amounts of breast milk in the same container
  • Use storage containers that are not meant for breast milk storage
  • Use breast milk that has been in the fridge for longer than a week

Portable Breastmilk Milk Cooler

Portable Breastmilk Milk Cooler

Store up to 16 oz of milk at a safe temperature for up to 24 hours with our new patent-pending Portable Breastmilk Cooler. 
It's the breastmilk chiller you'll bring everywhere.

Bags vs Containers

Breast milk storage bags are great because they can be stacked in your freezer and do not take up as much space as containers. They also are perfect for on-the-go purposes. However bags are more susceptible to tears and leaks, especially if they spend a long time in the freezer. Bags are also more difficult to measure how much milk you are actually storing.

Containers offer a clear way to see how much milk you have pumped and stored. With screw-on, airtight lids they are generally safer for breast milk storage in the freezer. On the other hand, containers take up more space when traveling or in your freezer.

How to Defrost Breast Milk

Thaw breast milk from the freezer by putting it in the refrigerator overnight. Be sure to thaw the oldest breast milk first. Thawing frozen breast milk in the refrigerator can take up to 12 hours, so it is important to plan in advance. Do not thaw breast milk at room temperature, or thaw in the microwave.

A small percentage of moms may experience milk with a somewhat sour, soapy scent once it is thawed; this is not harmful to your baby. The smell is due to the presence of lipase, which is an enzyme that helps break down fats. For these moms, when breast milk is kept at room temperature or in the refrigerator, their active lipase enzyme will create a stronger scent. The longer this breast milk is stored, the more lipase activity will occur.

Excess lipase activity is not a problem, but the aroma may be uninviting for your baby. To prevent this problem you can scald your milk which is a process of boiling milk before storing it in the freezer.

Breast milk can go bad most often due to chemical oxidation. If your stored breast milk smells rancid and more sour than normal, it is likely not salvageable. Breast milk also separates when it is stored and if it does not mix back together easily when shaken, this likely means that it's time to toss it out.

How to Warm Your Stored Breast Milk

It isn’t necessary to warm breast milk, but it all depends on your baby’s preferences. To warm the milk, put your milk container in a pot of warm water for a few minutes, or run it under warm water. To avoid any contamination, don’t let the water get on the seal of the container. Be careful to not microwave the breast milk. Microwaves can destroy nutrients and heat the milk unevenly, so unexpected hot spots can occur and burn your baby’s mouth or throat. Heating under warm water allows for more control on the temperature of the milk.

When done properly, storing breast milk in the freezer can be a stress-free and simple process that allows you to have a back-up supply for your baby when you aren’t around. To learn more about the benefits of breast pumping and storing, visit us, or head to our Instagram to join the Willow community.

The content provided here is for informational purposes only and is not intended to replace the advice of medical professionals. It should not be used to diagnose or treat medical conditions or problems. Please contact your healthcare provider with questions or concerns.
Which pump is right for you?
Which pump is right for you?

Which pump is right for you?

Which pump is right for you?

Which pump is right for you?

Which pump is right for you?