How to Properly Store Breast Milk

Breast Milk Storage Guidelines

It's important to properly store your expressed breast milk to ensure safety and maintain freshness. Breast milk should be stored in breast milk storage bags or clean, food-grade containers with tight fitting lids. Make sure to label your breast milk with the date and how many ounces, and also include your baby's name if you plan to send milk to day care.

Note: Breast milk storage bags include markers for measurements, but these can be somewhat inconsistent depending on how the bag is positioned or how much air is in the bag, etc. So I'd recommend pouring your milk into a bottle to measure the ounces before transferring to a bag, just to make sure you're consistent!

Freshly Expressed Breast Milk

How to handle your expressed milk depends on the type of storage you're using--at room temp, in the fridge, or in the freezer. A helpful tip you can use is the 4x4 rule for freshly expressed milk.

At room temp, your milk is considered safe for 4 hours.

If in the fridge, it's good for 4 days.

For frozen milk, you can safely store it in the freezer for 6-12 months. (Although closer to 6 months is preferred.)

Thawed from Frozen Breast Milk

When it comes to previously frozen milk, you should use it within 24 hours of being thawed, and within 2 hours of being warmed. We consider milk "thawed" as soon as the last ice crystals have melted. Once your milk is thawed, it has to be consumed within those 24 hours or used for other purposes, but you should never refreeze frozen milk.

Leftover Breast Milk from a Feeding

Once your baby begins to take a bottle of milk, it's recommended to use it within 2 hours, so if your baby doesn't finish a bottle, that milk should not be reused for a later feeding. It can be hard to predict how much your baby will drink, so to avoid wasting any milk, try storing your milk in varying or smaller amounts so you don't have to thaw more than you need. You can even use a silicone tray with 1 or 2 oz. portions to freeze small amounts of milk to top off a bottle if you think your baby needs more but you don't want to thaw a whole bag. I'll link all of my favorite breast milk storage items at the bottom of the post for ya!👇🏽

Thawing and Warming Breast Milk

When thawing breast milk, always thaw the oldest milk first. If you're planning ahead for later use, you can thaw the milk in the refrigerator overnight. Otherwise, you can run the milk under lukewarm water or put it in a bowl with lukewarm water on the countertop to thaw.

Sometimes storage bags can leak, so I'd recommend putting the bags in a clean bowl in the fridge just in case!

Once thawed, you don't need to warm the milk. Breast milk is perfectly safe to serve cold, and some babies are fine with that or even prefer it. But if you'd like to warm it, you can run the bottle under warm water or put it in a bowl of warm water. Otherwise, you can use a bottle warmer of your choice.

Bonus Tip! If you're struggling with bottle refusal, one trick I sometimes recommend is to try experimenting with milk temperature. For some babies, especially teething babies, cold milk is more easily accepted than warm!

Just remember to never put breast milk in the microwave. Not only can this damage the properties of the milk, but microwaves do not heat evenly so there can be hot spots in the milk that can potentially burn your baby.

Mixing Breast Milk

Breast milk is a complex fluid and it's constantly changing to meet your baby's needs, so the make up of your milk varies depending on time of day, your baby's age, whether you or baby is sick, etc. For this reason, many parents prefer to keep all pumping sessions separate, or to only feed PM pumps at night or AM pumps during the day. Mixing milk from multiple different pump sessions is considered safe and is sometimes preferred by many parents for convenience, so it's ultimately up to you!

Pooling milk from multiple different pumping sessions over a set period of time, also known as the pitcher method, has been shown to decrease the variability in nutrient and calorie content without increasing bacterial count in the milk. To use the pitcher method, you would simply combine all of your pumping sessions within a given period (usually 24 hours) and then distribute that milk into bottles or bags for feeding or freezing. You can also just combine one or two smaller volume pump sessions to create a single bottle for your baby. Just make sure when storing mixed milk collected over multiple days that you always label it with the date of the first pumping session. So for example, if you have milk from May 6 & May 7 that you're mixing, you should date it all the 6th.

The CDC does not recommend mixing milk of different temps due to the potential for bacterial growth when the fresh milk rewarms the cold milk upon mixing. With that said, the evidence in the literature really doesn't support this theory of bacterial growth, so it's ultimately up to you to decide what you're most comfortable with. To comply with CDC recommendations, you can simply chill all of the milk in the fridge before mixing. It's also acceptable to mix previously frozen breast milk with fresh breast milk but again, the CDC recommends chilling the fresh milk before mixing with the thawed milk. And remember, once mixed with thawed milk, it should be used within 24hrs from when the frozen milk was thawed.

Stayed tuned for more if you've got questions about pooling/mixing milk. I'm working on another blog post going over all the details that I'll share very soon!

Final Thoughts...

Managing your breast milk, especially if you're a busy working mom that is pumping often, can be a bit of a chore. Finding a good system that works for you can help streamline the process. You can find all of my top recommended breast milk storage supplies at the links below to hopefully help make your life a little easier!

Plus, you can also find a link to my free Breast Milk Storage Guidelines printable PDF below as well! You can print it and keep it on your fridge or in your pumping bag as a quick reminder for safety guidelines for breast milk storage! ⭐️

Download the Breast Milk

Storage Guidelines PDF here!

Shop storage supplies here!

Feeling like you need more in-depth help with feeding your baby? I'm here to walk beside you on your feeding journey with my Bottle & Breastfeeding Course! It's full of comprehensive, evidence-based strategies for feeding your baby to help you feel more confident and prepared. Click the link below for more!

Access the Bottle & Breastfeeding Course Here!