By moms. For moms.

Breast Milk Storage: Tips for Freezing and Refrigerating

Breast Milk Storage: Tips for Freezing and Refrigerating

Tips for freezing and refrigerating breast milk

Tips for freezing and refrigerating breast milk

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 patented, award-winning hands-free pumping bras and tanks, which can be used with all standard pump flanges, will help too!)

Know any other great guidelines for storing breast milk? We’d love to hear them. Please drop us a line below!

human milk mother's milk bags

Breast Milk 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:

Milk storage bags - Specially designed milk bags are the most popular milk storage option. They're inexpensive, and they don’t take up a lot of room in the fridge or freezer. Our Breast Milk Storage Bags are easy to use, transport, store, and warm, and they’re compatible with all major breast pump brands.

Glass - The Cleveland Clinic recommends glass containers because they best preserve the components of breast milk. But since glass can break easily, some child care centers won't accept glass containers.

Plastic bottles or containers - Hard-sided, clear, plastic containers, like the bottles that often 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.

BraveMom Tip: Double bag your milk to save any milk that may leak if the original bag gets damaged in the freezer. Some parents store a few milk storage bags in a bigger storage bag.

Breast Milk Storage

How much milk should I store in each container?

Since breast milk expands when frozen, storing milk in 2-4 ounce increments will help prevent overfilling your bags (or thawing more milk than you need for a feeding). This amount is also easy to thaw and warm up quickly.

Do I have to sterilize baby bottles/storage containers?

According to the CDC, if your baby was premature, is less than three months old, or has a weakened immune system, it's 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 hot water and a heated drying cycle, sterilizing may not be 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 of your 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, Lactation Counselor, and IBCLC 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

Breast Milk 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 freshly expressed milk within 3-5 days, you don't 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 3 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.

Freezing and Thawing Breast Milk

How long does thawed breast milk last?

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

Can I refreeze thawed milk?

According to KellyMom, if your previously frozen milk contains ice crystals and has not completely thawed, it is still considered frozen and is therefore safe to refreeze. Some research suggests that you may even be able to refreeze completely thawed breast milk. A 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 before freezing. Make sure to write the date of the first milk on your label (base the expiration date on the oldest milk).

plastic bags for breast milk

Breast Milk Thawing and Preparation Questions

How do I thaw frozen breast milk?

The simplest way to thaw frozen milk is to put it under warm running 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. 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.

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.

Breast Milk Storage

Do I need to heat up breast milk?

No. Some parents 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?

We're often asked some variation of "Is this breast milk still good if...?" If your milk spoils, there will be a distinct foul odor. Refrigerated or frozen milk often separates into fatty and non-fatty layers, but if it remains chunky when swirled, it may have gone bad. Breast milk color can vary quite a bit, so it’s not a great indicator.

If it’s been in the fridge for more than 3 days, hanging out in the door or at the front of the fridge, the milk may have 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 don't 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 of containers of your thawed milk before freezing large volumes, just in case you have high lipase milk.

benefits of breastfeeding

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.  

Please note that these suggestions are for educational purposes only. They should not replace medical advice. They are also intended for healthy, full-term infants; if your baby was premature or is immunocompromised, other milk storage guidelines may be indicated. For more information about pumping and storing breastmilk, please contact your pediatrician or local Department of Health.


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. Bring your favorite pumping-at-work sign, your pump bag, your ice packs, and one of our pumping & nursing bras – and pump on (whether you choose a milk bottle or bag)!

door hanger for privacy while pumping at work
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