This post may contain affiliate links. Please read my disclosure for more info.

Want to know more about freezing breast milk?

Yeah, you do.

Now that you’re pumping it’s essential you know your options for storing your breast milk. Need some breast milk for tomorrow? Pop it in the fridge. Want to build a breast milk stash? Freeze that liquid gold.

Now, you don’t need a freezer stash of breast milk. But, I like to think it’s a great insurance plan when you’re breastfeeding.

Think about it, do you have a plan B if you need breast milk in an emergency? Say your milk supply drops, or you need to take medication you can’t breastfeed with?

You’ll sure be glad you have a freezer supply of breast milk to use.

In fact, freezing breast milk is a great way to store anything you pump for longer than a week.

Your pumped breast milk is precious, so you’re going to want to freeze it properly. There are a few steps involved, but I’m going to talk you through them. Plus I know you have lots of questions right?

Just a heads up. Any advice in this guide applies to full-term, healthy babies. If your baby is born premature or sick, please discuss storing your breast milk with their doctors or nurses. You may need stricter storage rules to keep the milk safe for your baby.

Let’s get started.

Choose a Storage Container

Before you learn how to freeze breast milk, you’ll need to decide on the storage container you’ll use. What’s the best way to store frozen breast milk? Well, that depends on your situation. Let’s look at the most popular storage options and which one will suit you best.

Breast Milk Bottles

The collection bottle that attaches to your pump, can be used to freeze your breast milk.

It’s pretty simple. Pump, pop on a lid and put the bottle in the freezer. Then defrost when needed and feed it to your baby.

Because you are using the same bottle for the whole process, it cuts down on washing (woohoo!). It’s also hygienic as there are fewer surfaces that the breast milk touches.

Also, you don’t need to buy any additional storage containers, which save you some moolah.

Yeah, this is sounding pretty fricking good right? Well, there is a drawback.

Bottles take up a lot of room in your freezer. Honestly, I’d only recommend using bottles if you have a small supply you want to freeze. Or perhaps if you’re on a tight budget.

Remember that if your collection bottles are all stored in the freezer, you’ll have less to pump into.

Oh and one more thing I’d suggest is to use glass bottle (like these) to freeze the milk. You’ll need sealing caps to replace the nipples for storage. Why do I recommend glass bottles? Well, you don’t want plastic chemicals to leach into the breast milk, especially the longer you store it for. If you think I’m being too crunchy, at least make sure your bottles are BPA free.

Breast Milk Bags

What? You get special bags just to store your breast milk.? Crazy right. Now I know you think these are one of those unnecessary parenting products.

But hear me out.

Don’t be tempted to use regular freezer or zip-lock bags. Breast milk freezer bags are designed to be sterile and leak proof when in storage. This is essential to keep your milk safe for your baby.

The best way to use them is by freezing them flat. That way they take up very little space. That’s why freezer bags are the best way to store a larger stash of breast milk. You need these if you plan to use a lot of frozen breast milk.

The biggest drawback of using these bags is they are single use. Now that adds up to a nice chunk of change over time if you need to buy a lot. Be smart about it and buy them in bulk if you know you’ll be using them anyway.

Remember you’ll need to thaw all the milk you store. If you pump a total of 5oz into a bag and freeze it, you need to thaw the whole lot. That means you may end up wasting some milk if your baby doesn’t drink it.

I’d highly recommend using a brand that you can pump directly into and then freeze. I wish I had something like the Kinde System to use when I was pumping. I would have gladly paid to save the time you waste to decant the milk and wash collection bottles.

Milk Freezer Trays

Do you hate wasting food? Ooohh I hear ya.

What about when you’ve had to wait 30 minutes for it to drip out your breasts? Just the thought of it wasting it gives you the fear.

You need some milk freezer trays.

These freezer trays are like little ice cubes trays for breast milk. These ones are my favourite. You save your milk in 1oz portions, so it cuts down on waste. You only need to thaw the amount of milk your baby usually takes, and there should be minimal leftover.

This biggest disadvantage is that you will need to decant the milk from the collection bottle. That’s a bit of a pain for washing up. Unless you want to hand express into the trays.

I’d recommend you store the frozen portions in a larger freezer bag or tub to keep a large supply. It’s great just to grab the number of ounces you need and thaw in the bottle. It also means you can refill the tray one the milk freezes.

These freezer trays are also great for when you start weaning your baby onto solids. You can use them to freeze small portions of batch cooked baby food.

Popsicle Molds

This option isn’t a long-term storage solution. But I thought I’d mention it anyway.

A baby popsicle mold is perfect for making little breast milk pops for your teething baby. The breast milk soothes them, and the cold gives your baby a lot of relief for their sore gums.

If your baby is beginning to sprout a few pearly whites, consider using some of your expressed milk this way.

I love these Nuby Popsicle molds. The handle is easy for your baby to hold. Plus the mold makes a pop just the right size for your baby.

How To Freeze Breast Milk

Now you’ve got your storage containers let’s discuss how to freeze your breast milk. I’m going to start right at the beginning, so you know the safest way to collect and freeze your breast milk.

1. Hand Hygiene

Freezing milk doesn’t kill any bacteria. Remember before you start pumping, always wash your hands . This simple step prevents any contamination getting into your baby’s milk. If you’re not near a sink, keep a stash of alcohol hand sanitizer to use as a backup.

2. Filling the Container

If you are pumping directly into your storage container, don’t fill it to the top. Leave a bit of room. The same applies if you are decanting the milk from the collection bottle into a bag.

You need to leave space so your milk can expand as it freezes. If you don’t, the breast milk may leak from the container. And yes, you will be crying over spilled milk.

3. Seal and Label

As soon as you are finished pumping (and decanting) seal the storage container. Depending on your chosen method this will be:

  • Bottles– Don’t use a bottle nipple to seal. You need a solid, flat storage lid that screws on to give the best seal.
  • Freezer Bags – These are usually zips or snap lock. Make sure you firmly close the seal all the way along.
  • Freezer Trays – Snap the lid in place. Again make sure the seal is closed tight all the way around.

Use waterproof ink to mark your stash with the collection date and time. It will make it easier for you to rotate your supply. You’ll also know how safe it is to use for baby depending on storage times.

It’s important to add your baby’s name if you are storing the milk in a shared facility such as a neonatal unit, to prevent mix-ups.

4. When To Freeze breastmilk

Your milk will be warm after you pump it. Give it a few minutes to cool down to room temperature. Then put it in the freezer. Your breastmilk will be as fresh as possible.

If you can’t get a freezer straight away, don’t worry.

You can keep your breast milk at room temperature for 4-6 hours (2-4hrs if it’s a hot room). Be sensible and try to keep the milk as cool as possible. A cooler bag will keep your milk safe 24 hours.

Ideally, without a freezer, store it in a fridge to keep it cool as possible. The milk will keep good in a fridge for up to a week.

5. Where to Freeze Breast Milk

Place the milk container at the back of the freezer, as far away from the door as possible.  If you can keep them in a separate compartment that  you won’t open often.

Every time you open and close the freezer door to grab your Ben and Jerrys, this causes a temperature rise. Your milk will slightly thaw and refreeze each time, which can make the milk go off.

Keep in mind basic food hygiene too. Don’t go storing your breastmilk underneath or beside frozen meats. Your baby has an immature immune system, don’t go making them ill.

You might want to store freezer bags, lying flat in the quick freeze section. Once they have frozen solid, you can move then store them upright to save space.

6. How Long to Freeze Breast Milk

Any freezer is suitable for your breast milk. However, it will affect the length of time it can safely store it.

When talking about food safety, it’s always good to know what the official advice is. That way you know I’m not giving you some random figures I’ve pulled out the air. The American Association of Pediatrics recommends these times for safety:

  •     Small freezer compartment for up to two weeks
  •     Freezer (<4°C, <39°F) for 6 months
  •     Deep freeze (-18°C, 0°F) for 12 months

7. Using Your Freezer Stash

It’s always best to use the oldest milk first. If that milk is out with the safe storage times, use the oldest container that is in date.

If you’ve not kept a well-organized system, you’ll need to check the label dates.

I’d recommend saving yourself the time and keeping well-organized. Handy organization containers like these have a first in, first out system and your stash well rotated. Plus they keep your stash protected from your other freezer contents.

Pin For Later

Breast Milk Storage Tips | Want to know how to freeze breast milk safely? Storing breast milk is essential for pumping moms. Keeping the milk safe enough for your baby to drink when you need it. Learn how to start freezing breast milk. Plus find out what storage method is best for you, bottles, freezer trays or freezer bags.

FAQ about Freezing Breast Milk

Does freezing affect the milk?

Obviously, fresh breast milk is best for your baby. But freshly frozen breastmilk won’t do them any harm.

The bigger issue with freezing your milk is that your breast milk constantly changes to adapt to your baby’s nutritional needs. That’s amazing, right? Yeah, but it also means milk that you express when your baby is three months old will be nutritionally different from fresh milk expressed at six months old.

Any frozen breast milk will always be nutritionally better for your baby than formula.

A study* found that frozen breast milk stored for longer than three months loses some of its fat and calorie content. That’s why you need to use ‘oldest’ milk first when using up your frozen milk supply.

If you plan to keep your milk for longer than three months, I’d highly recommend a deep freeze. The lower temperature will keep the nutrients in your milk for longer.

Other studies which have found freezing milk slightly reduces the vitamins A and C content. However, frozen breast milk still has enough to meet your baby’s requirements.

How to thaw frozen breast milk

The safest way to defrost your breast milk is to place it in a refrigerator overnight or around 12 hours before use. It’s the best way to keep all the essential nutrients of the milk and prevent bacteria activity.

If you need the milk quicker, you can speed up the process by running the container under water. Start with cool temperature and gradually increase until the milk is warm.

How to warm up breast milk

Always thaw your breast milk before heating.

If you heat frozen milk directly, you risk losing essential fats and vitamins in the milk. Your baby may drink the milk cool. Don’t be surprised if they don’t like it. Your baby will prefer it to be around body temperature (98.6 F / 37 C).

To warm the thawed milk, start by pouring the milk into your feeding bottle. Put on the bottle nipple and lid.

Fill a kitchen jug with warm or hot water. Put the feeding bottle into the jug and leave for a few minutes. Every minute or so, remove the milk swirl in a tornado motion (don’t shake) and test the temperature on your hand. The perfect temperature is when the milk is neither hot nor cold.

If you are short on time, you can use an electric bottle warmer to heat the milk. These are great for heating the milk at a constant temperature. Their timers are great, so you can get extras tasks done in between waiting for the milk to heat, without worrying it will overheat. You can check out my bottle warmer recommendations here.

Never heat a bottle in a microwave or directly on a stove. Seriously don’t be tempted, thinking it will heat quicker. It’s dangerous. The milk doesn’t heat evenly and creates heat pockets which can scald your baby’s mouth as the feed.

Mixing fresh and frozen breast milk

If you’ve just expressed some milk, but have a supply of frozen milk, you can mix them.

Make sure your frozen milk if fully thawed first. Then heat the frozen milk to body temperature. Swirl the milk together to get a good mix.

Refreezing thawed breast milk

It’s not recommended you refreeze any thawed breast milk. Also don’t re-heat thawed milk more than once. Re-Heating and re-freezing any foods aren’t good for contamination reasons.

You can keep thawed milk in the refrigerator for up to 24 hours before using.

Does frozen breast milk sour?

When you’re milk freezes, it separates into fatty layers. This can give the milk slightly soapy smell. It might also look watery, compared to when you pumped. The milk is safe to use unless it been stored too long or it smells off.

Can I freeze breast milk if I have an infection?

If you have breast thrush, it’s safe to give your baby frozen milk while you get treated. As long as the milk was not pumped when you had thrush.

Freezing doesn’t kill the yeast which causes thrush. That means you should throw away any breast milk you expressed and froze while your thrush was active.

If you have mastitis, it is ok to freeze breast milk as long as you are not taking antibiotics. It’s important to remember your breast tissue is infected, not your milk.  Quite often antibiotics give your milk a metallic taste, which your baby may refuse.


Freezing your breast milk is a great way to keep a stash for your baby. You never know when you may need it. Just like storing any food you need to know how to store it safely. It will keep your baby safe from contamination. The storage method has to work for your pumping routine and your family’s home life.

If you found this post helpful, please share with other moms who may find it useful. Remember you can leave a comment below and let us know your tips and tricks for freezing breast milk.