Brave New Motherhood
Everything You Need to Know About
Breast Milk Storage

How to Store Breast Milk

Breast Milk FAQs

Breast milk is one of the greatest gifts you can give your baby. That’s why you pump during your lunch break or in the middle of the night and why you really do cry over spilled (or spoiled) milk. Since you devote so much of yourself to pumping milk for your baby, you want to make sure you’re storing and using it correctly. We put together some answers to the breast milk storage questions we get most often. We hope this information will help you give your baby all the nutrients your amazing body has produced. (Our award-winning nursing bras and new and improved hands-free pumping bra will help too!)

Know any other great breast milk storage tips? We’d love to hear them. Please comment below!

Container Questions

What containers do I need for storing breast milk?

There are a few options you can choose from depending on your personal preference and lifestyle:

Glass: The Cleveland Clinic recommends glass containers because they best preserve the components of milk. Glass containers are easily reused and don’t contain the harsh chemicals certain plastic storage options may have. While glass does preserve more antibodies, it may not be the best option if you frequently transport your milk.

Plastic bottles or containers: Hard-sided, clear, plastic containers, like the bottles that come with double electric pumps, can also be used. These bottles are reusable and unlikely to break. It can, however, be costly to have the number of bottles you need to store all your milk.

Milk storage bags: Specially designed milk storage bags are the most popular milk storage option. They are inexpensive and easy to transport, and they don’t take up a lot of room in the fridge or freezer. BraveMom Tip: Double bag them to save any milk that may leak during thawing if the original bag gets damaged.

Breast Milk Storage

How much milk should I store in each container/bag?

Storing milk in 2-4 ounce increments will help prevent wasted milk. You can also quickly thaw and warm up this amount.

Do I have to sterilize baby bottles/storage containers?

According to the CDC, if your baby is a preemie, is less than three months old, or has a weakened immune system, it is important to wash and sterilize your bottles and breast pump parts daily to keep germs and bacteria at bay. Daily sterilizing may not be necessary with a healthy, older infant, but you might want to sterilize weekly. If you use a dishwasher with a hot water and heated drying cycle, then sterilizing is not necessary. BraveMom Tip: Don’t forget to clean the exterior face and knobs of your pump. You can also wipe down the exterior of your tubing. You don’t need to wash the interior tubing since it does not come into contact with breast milk; if you notice bacteria growth or dirt inside the tubing, replace it.

How do I sterilize my bottles and pump parts?

According to Registered Nurse and Certified Lactation Counselor Shantel Harlin, first, wash the bottles and pump parts that come into contact with your breast milk. Once these are clean, you can sterilize your parts by using specially made steam sterilizer bags or by placing your parts in a pot of water and boiling them for 5 minutes.  When the parts are sterilized, place them on a clean, dry towel to air dry.

Cleaning Pump Parts

Timing Questions

How long can I leave freshly expressed milk out?

Freshly expressed breast milk in a closed bottle can be left out at room temperature for 4-6 hours.

How long can I refrigerate freshly expressed milk?

You can store your fresh milk in the refrigerator for 3-5 days.

Do I need to freeze my breast milk?

If you plan to use the milk within 3-5 days, you do not need to freeze it. Just be sure to label your milk with the date so you know when it expires. For tips on keeping milk cold while traveling, check out our blog, and for tips on using dry ice in a cooler, check out this blog.

Can I freeze milk that’s been sitting in the fridge for a few days?

You can refrigerate milk for 3-5 days and move it to the freezer any time before that period is over. To preserve the most nutrients, however, it’s best to freeze milk as soon as possible, ideally within the first three days. Keep your milk in the back of the fridge, where it is less likely to be affected by temperature fluctuations from opening and closing the door.

How long does frozen breast milk last?

Ideally, you will use your frozen supply within 3-6 months, but it is safe for consumption for up to 12 months if stored in a deep freezer.

How long does thawed breast milk last?

Once you thaw frozen milk, it can be refrigerated and used for up to 24 hours.

Freezing and Thawing Breast Milk

Can I refreeze thawed milk?

According to KellyMom, if your milk contains ice crystals and has not completely thawed, it is still considered frozen and is therefore safe to refreeze. New research suggests that you may even be able to refreeze completely thawed breast milk.  A 2016 study published in Breastfeeding Medicine found no bacterial build-up or significant nutritional decrease in breast milk that had been completely thawed in the refrigerator for up to eight hours and then refrozen.

Can I reuse breast milk my baby didn’t finish?

According to some sources, like the Cleveland Clinic and KellyMom, it is probably safe to feed babies leftover milk up to 2 hours after the initial feeding. If possible, refrigerate the leftover milk between feedings. You can offer this milk at the next feeding (before the baby’s mouth bacteria has a chance to grow in the milk), but after that, it should be discarded.

Can I combine milk pumped at different times into the same storage container before freezing?

It’s perfectly safe to combine expressed milk from different pumping sessions into one storage container prior to freezing. According to Harlin, lactation consultants typically recommend the different milk be the same temperature before combining. For example, if you have 2 ounces of milk in the fridge and 2 ounces of freshly expressed milk, you can cool the fresh milk, and then put it in the same container as the refrigerated milk; you can then freeze the 4 ounces or use them for a feeding. Make sure to write the date of the first milk on your label (base the expiration date on the oldest milk).

Preparation Questions

How do I thaw frozen milk?

The simplest way to thaw frozen milk is to run it under warm water for a few minutes. Gently swirl the bottle to mix the components and test the temperature by squirting a few drops onto your wrist. You can also use a bottle warmer or put the frozen milk you will be using the next day in the refrigerator overnight.

Can I heat milk on the stove?

No, but you can heat a pan of water on the stove, remove it from the heat, and then place the milk container into the warm water. Keep in mind high heating can lower nutrient values, so you don’t want the water boiling hot. You can also heat water with a kettle and pour it into a bowl. When the water is warm, not boiling, place the container of milk in the bowl to thaw.

Breast Milk Storage

Why can’t I microwave milk?

A microwave does not heat evenly, which can result in potentially dangerous hot patches in your breast milk. Microwaves can also destroy important nutrients in breast milk and cause bottles to leach chemicals or explode. That said, you can warm up water in a bowl in the microwave and then place your container in that warm (not boiling) water.

Do I need to heat up breast milk?

No. Some moms like to warm milk to make it seem more like milk straight from the breast, but many babies don’t mind colder temperatures. British parenting organization First 1,000 Days says there is no scientific evidence that milk straight from the fridge hurts the nutritional content or digestive properties of breast milk.

How can I tell if breast milk has gone bad?

If your milk spoils, there will be a distinct foul odor. Stored milk often separates into fatty and non-fatty layers, but if it remains chunky when swirled, it may have gone bad. If it’s been in the fridge for more than 3 days, hanging out in the door or at the front of the fridge, it’s possible the milk has gone bad sooner than the maximum shelf life – especially if the container wasn’t fully sealed. The most conclusive way to tell if breast milk has gone bad is to taste it for a sour, “off” flavor.

A slightly metallic or soapy odor coming from stored milk, however, is related to higher levels of the lipase enzyme; although this enzyme is not harmful, many babies do not like how this milk tastes when thawed. If your milk has high lipase, scald it before freezing to eliminate the soapy taste. BraveMom Tip: Test a couple containers of your thawed milk before freezing large volumes, just in case you have high lipase milk.

Your Liquid Gold

We hope this information helped answer your breast milk storage questions. Be sure to download the infographic below; print it out and put it on your fridge! We know what a commitment (an act of love, really) pumping is, and we want it to be as comfortable and productive a part of your breastfeeding journey as possible. Successfully storing your liquid gold will ensure your baby gets the perfect food for him or her.  

Please note that these suggestions are for educational purposes only and should not replace medical advice. They are also intended for healthy, full-term infants; if your baby is premature or immunocompromised, other storage guidelines may be indicated. 

breast milk storage

PS: We designed super-cute, printable door hangers in case you pump at work. Click on this link or the button below to download and print them. Pump on, Mama!

door hanger for privacy while pumping at work