Here’s what you need to know about storing your milk at room temp, in the fridge or freezer, and on the go. 

Unless you’re pumping and bottle feeding right away, you’ll need to have a plan for storing your breast milk safely — whether you’re at home, at the office, or on the go. There are products to stock up on (think: storage bags, insulated coolers, ice packs), guidelines to follow, schedules to consider, and more! 

So we spoke to Dr. Laurie Jones, a pediatrician, breastfeeding medicine specialist, and the founder of Dr. MILK, to get her top tips for any mom looking to build her fridge or freezer stash with peace of mind. Read on for everything you need to know about storing your milk at any temperature! 

We’ll cover: 

• The basics of milk storage
• Best practices to follow 
• What to do when you’re ready to thaw 
• What to do if you store more than you can use

The basics of milk storage 

These guidelines from the Centers for Disease Control (CDC) and Academy of Breastfeeding Medicine (ABM) are recommended for freshly expressed breast milk for healthy, full-term babies. Always check with your pediatrician if you’re unsure about what’s best for your baby!  

In addition to paying close attention to the temperature and duration of time, Dr. Jones emphasizes the importance of clean storage conditions, which will minimize the risk of bacteria growth.

Best practices to follow

Now that you’re up to speed on the recommended guidelines, here are a few ways that you can make milk storage easier and minimize the spread of harmful bacteria.

Keep everything clean 

Wash your hands before and after pumping. Between each session, wash your pump parts in warm, soapy water and let dry completely. You can save time by keeping extra sets for your Willow Go and Willow 360 on hand. Just rinse after each use, and then batch clean and dry them once a day. Willow offers an all-in-one cleaning kit, too, perfect for pump parts, bottles, and more!

Handle it quickly 

The longer your milk is sitting out at room temperature, and the more times that you handle it, the greater the risk for bacterial contamination. Aim to transfer your milk as quickly as possible before putting it in the fridge or freezer — and if you need to transfer it again (say, by pouring it into a glass pitcher from a storage bag that you brought home from work), do it as quickly as possible. 

This will also ensure that your baby is getting as many nutrients as possible, Dr. Jones explains. With milk fat clinging to bags and bottles, the more you transfer milk between containers, the less fat your baby is likely to get!

Store it safely 

Pump directly into milk bags, or pour your pumped milk into milk storage bags, pitchers, or an insulated breast milk cooler. Cleanliness is paramount here as well — make sure that any surface you’ll be handling milk on (like your kitchen counter or desk) has been wiped down and is free of any open food or drinks. 

Keep track of the time and date

Label it with the date and number of ounces pumped, then store it on the countertop, the refrigerator, or the freezer. This is how you’ll keep track of how long your milk can be stored before it needs to be fed to your baby or discarded. Always use the oldest milk first!  

Store in serving sizes 

Get the most out of what you pump by keeping it in serving sizes that make sense for your use. If you are away from your baby for a single daytime feeding session, for example, you might simply fill a 4-ounce bottle with pumped milk (and freeze whatever remains from your pumping session). 

Label and organize it 

Label your pumped milk with dates and ounces. For short-term storage in the refrigerator, you’ll want to ensure that the milk you serve is as fresh as possible. For long-term storage, the CDC says you can freeze breast milk for up to 12 months, though thawing and feeding it to your baby within 6 months is optimal. 

Freeze it like you mean it 

Try to freeze your milk bags flat and away from the high-traffic areas of your freezer (they can break easily), ideally in a colder section to ensure longevity. Place them in chronological order so you can easily use them in that order. And if for some reason the bags should thaw (i.e., during a power outage), use them or lose them. 

What to do when you’re ready to thaw 

Because defrosted breast milk must be consumed or thrown out within a day (depending on where and how you’ve thawed it), it’s important to only thaw what you need! 

Taking the time to thaw your breast milk the right way is essential. Not only will it help you preserve important macronutrients, vitamins, and minerals, but it will also prevent bacterial growth and ensure that your milk is safe for your baby. Unfortunately, bacteria can grow and spread in breast milk pretty quickly if it isn’t handled properly!

How to thaw 

• Milk can be thawed in the refrigerator. It will take between 4 and 12 hours to defrost completely. Always thaw bags standing up to avoid leaks, and use containers. 
• Milk can also be thawed under a stream of warm water, or by being placed in a bowl of warm water. If using a bowl, swirl gently to speed defrosting and to make sure that the fatty parts of the milk (which may separate when frozen) are incorporated. Make sure the temperature is no higher than 99 degrees. Never microwave breast milk! 
• Fully defrosted milk can remain in the fridge for up to 24 hours, or at room temperature for two hours, before being used. 
• If thawing milk still has ice crystals you can refreeze it, but any completely thawed milk that has been previously frozen should never be refrozen. 
• Any breast milk that has been mixed with powdered or liquid formula should be used within an hour. Any milk left over should be disposed of. 

You can learn more about thawing your breast milk safely here.

Quick tips

Tip #1: You’ll know that your breast milk is fully thawed when it is liquid and chilled. It’s okay if you notice a couple of remaining ice crystals — these will likely dissolve quickly once your milk is poured into a bottle.  

Tip #2: Before serving, swirl the milk gently to incorporate any fat that has gathered on the side of the container. Milk that has been warmed (under running water or by your hand) will swirl more easily.

Tip #3: If your milk smells rancid or excessively sour once defrosted, that’s an indication that it has gone bad,” or spoiled due to chemical oxidation.  

What to do if you store more than you can use

If you find you’re storing more pumped breast milk than you’re going to use, consider donating it. Your breast milk will need to go through a screening process to check for pathogens and viruses before milk banks accept it. The Human Milk Banking Association of North America can help you get started. 

If you regularly travel away from your baby for a duration of time that makes storing it untenable (more than 24 hours) and need to pump, consider donating or shipping your pumped milk home using services such as Milk Stork. 

Now you’re ready to store your milk safely! 

For more tips about safe milk storage, check out the Pumping and Breastfeeding section on our blog, and explore milk storage options such as our Portable Breast Milk Cooler.