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

TL;DR: Key Takeaways

Whether you’re at home, at work, or on the move, proper breast milk storage ensures your baby’s milk stays fresh, safe, and full of nutrients. Follow CDC and Academy of Breastfeeding Medicine (ABM) guidelines:

• Room temperature: Up to 4 hours (77°F / 25°C or colder)
• Refrigerator: Up to 4 days
• Freezer: Up to 12 months (best within 6)
  Always label milk, use clean containers, and thaw only what you need.
  

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! 

Table of Contents

1. The Basics of Breast Milk Storage
2. Best Practices to Keep Milk Safe
3. How to Organize and Freeze Milk
4. Thawing Breast Milk Safely
5. Quick Tips for Freshness
6. What to Do If You Have Extra Milk
7. Suggested Visuals

1. 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. Always consult your pediatrician for specific guidance if your baby is preterm or immunocompromised.

2. Best Practices to Keep Milk Safe

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.

✨ Pro tip: The Willow Cleaning Kit makes sanitizing pump parts and bottles quick and easy.

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). 

3. How to Organize and Freeze Milk

Label and organize it 

• Label each bag before filling to prevent smudging.
• Store freshly pumped milk at the back of the fridge where it’s coldest.
• When freezing, lay bags flat to save space and prevent cracking.

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. 

4. Thawing Breast Milk Safely

Defrosting your milk properly keeps it safe and nutritious.

Quick reference guide: 

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.

6. Quick Tips for Freshness

Tip #1: Fully thawed milk will be liquid and chilled. A few ice crystals are fine—they’ll melt quickly once warmed.

Tip #2: Swirl milk gently before serving to redistribute fat evenly.

Tip #3: If milk smells sour or rancid after thawing, discard it. This may result from oxidation or improper storage.

6. What to Do If You Have Extra Milk

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! 

By following proper storage, labeling, and thawing methods, you’ll preserve the nutrients in your milk and ensure your baby stays safe and satisfied.

✨ You worked hard for that milk, mama—make sure it stays as amazing as you are.

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 Breast Milk Storage Bags, Glass Breast Milk Pitcher and Portable Breast Milk Cooler.

FAQs

• How long can breast milk stay at room temperature?
  Freshly pumped breast milk can stay at room temperature (up to 77°F or 25°C) for up to 4 hours.
• How long does breast milk last in the refrigerator?
  Breast milk can be stored in the refrigerator for up to 4 days.
• How long can breast milk stay in the freezer?
  Breast milk can be stored in the freezer for up to 12 months, but using it within 6 months is best for nutrient quality.
• What is the safest way to thaw frozen breast milk?
  Thaw milk in the refrigerator for 4 to 12 hours. For faster thawing, place the bag under warm running water or in a warm bowl (under 99°F).
• Can thawed breast milk be refrozen?
  Only if ice crystals remain. Fully thawed milk should never be refrozen.
• How long does thawed breast milk last?
  Once fully thawed:
  • Up to 24 hours in the fridge
  • Up to 2 hours at room temperature
• Can I microwave breast milk?
  No. Microwaving destroys nutrients and creates hot spots that can burn your baby.
• How do I know if thawed breast milk has gone bad?
  Discard milk if it smells sour or rancid, appears clumpy, or does not mix smoothly when gently swirled.