How To Freeze Breast Milk | 10+ Things You Need To Know

If you are pumping breast milk, chances are, you will be freezing some of them.

But do you know how to freeze breast milk properly and efficiently?

There are conflicting info all over the Internet, articles, motherhood forums, so if you are new to this, it may look confusing.

I'm not an expert in this, but I thought I would share some knowledge that I've gathered about it throughout my pumping journey.

Remember, this is not a hard rule kind of thing.

There are quite diverse opinions on breast milk handling, so this may be different from what you've read so far.

What I share here is what works for me, and if you do this differently, feel free to share yours at the comment below the article.

This post is part of PUMPING AT WORK series. Other articles in this series.

• A Breastfeeding Mom’s Guide To Returning To Work After Maternity Leave
• How to build breast milk stash before returning to work
• 7 Ways To Collect Breast Milk With Haakaa
• How to Collect Breast Milk With Haakaa Even If You Don’t Leak
• How much breast milk stash do you need | A case study
• How to freeze breast milk | 10 Things You Need To Know
• How to rotate breast milk stash
• How to thaw and warm frozen breast milk 
• Breast milk storage systems | Milk Bag vs Bottle, Which One To Choose
• 10 tips on introducing bottle to breastfed babies
• How to maintain milk supply at work
• 30+ pumping hacks for working moms

1. What container is best to store frozen breast milk?

My take: option (1). It's easier to store the same amount, easier to track and choose which bag/ bottles to thaw for feeding.

Another note: I did use breast milk bags in the past and filled it up to 200 ml (so, 2 feedings for my baby) in order to maximize the milk bag capacity, but to be honest, I don't enjoy pouring milk from bag to bottle.

I feel that there's so much milk stuck on the bag and I can't help feeling sorry about those wasted milk.

OK, this is just my personal opinion, please don't feel offended if you are using breast milk bags.

3. Don't forget to label your frozen milk

Write down the date when the milk is expressed plus the amount of milk (if every bag is different amount).

Some mothers wrote down the both date and time, but I didn't do this because I mostly combine all the milk throughout one-day pumping.

Milk bag has a dedicated space to write these labels.

For bottles, you can use all-purpose label like this.

4. Don't forget to check for excess lipase issue

When your body produces excess lipase, some of it may transfer to your breast milk and affect how it tastes after refrigeration / freezing.

The milk may have a strong odor, metallic / soapy taste, some moms even described it as horrible taste, such that your baby reject your expressed milk altogether.

So, before you are storing more and more frozen milk, check if you have excess lipase issue.

I've seen it again and again.

Stories of mother throwing her frozen stash because it is not usable, her baby rejected it.

How to test for excess lipase and what can you do to solve this issue?

Rebekah has a great explanation in her video and even wrote a dedicated book to explain every single details about excess lipase and what you can do with your breast milk. Check it out here.

5. How to ensure that my oldest milk gets used first?

With milk bags, use an old shoe box /rectangular container and arrange your breast milk stash such that the oldest milk is put in the front.

Then, whenever you have a new stash, you put it at the very back end of the container.

Or, if you stack the milk bags vertically, use a dollar-store bag and slit a little hole at the base of your bag, put new milk on top, you take the oldest one from the bottom hole, pretty smart (see it in action here).

Alternatively, invest on a breast milk bag storage rack like this.

With bottles, I love to group 3 bottles into a ziplock bag, lay the bag horizontally and stack the bottles up. Since I use / store new frozen milk every day, I rearrange my breast milk stash every week such that the oldest is in front and the newest is at the back of the freezer.

6. Characteristic of frozen / refrigerated milk

When breast milk is stored in fridge / freezer, the fat will separate from the rest of the liquid forming the top layer (see the picture).

 This is fine and does NOT mean your milk is spoiled.

After thawing, you can just swirl the milk gently (no-shaking please), so it will blend uniformly again.

7. Don't fill the milk bag / breast milk bottle too full.

Liquid expands when it is frozen, and so does breast milk.

If you fill your bottle too full, your bottle cap may pop up suddenly due to the expansion. Similarly, your milk bag may burst because of this. 

I believe, you don't want that to happen, right. So, leave some extra room in your milk bags / bottles to make sure it can handle the expansion well.

Confession: YES, I experienced this problem, lol.

Luckily, I store my frozen bottles inside a plastic bag in the freezer. So, my milk was not immediately contaminated with other food stuff I put in the freezer.

8. Can you combine breast milk from different pumping sessions?

Yes.

The general rule is you can combine as long as they are within 24-hour period. 

Say, you pumped at 6 am, 2 pm, and 9 pm. You can combine milk from those pumping sessions and put the milk in one bottle / milk bag.

Confession: In extreme situation (such as when I didn't get 1 full feeding even after 24-hour pumping), I occasionally combined several days pumped milk, but labeling them with the oldest date. I didn't do it often, but I did.

9. Can you freeze refrigerated breast milk?

Yes.

The general rule is: If you don't intend to use it in the next 3 days, freeze it.

Usually I wait for a few pumping sessions so that I have accumulated enough for 1 feeding, then combine them and put in the freezer.

10. Can I put fresh pumped milk directly into freezer?

Some moms do this, but some source suggests to cool the milk in the fridge  first to avoid drastic temperature change.

11. Can I top up an already frozen milk with a cooled / chilled milk?

Yes, you can. Here's the resource that says so.

But in reality I've never done this, because I won't know accurately how much milk I'd have in that bag/ bottle.

12. When is the best time to combine milk before storing into freezer?

It's up to you.

You can wait for a few pumping sessions to get enough milk for one feeding, then it goes straight to freezer.

Personally, for practicality, I don't like combining milk and put it into freezer at my workplace.

So, I did it only once a day in the morning at home when I prepare milk for the nanny. Thus, the pumped milk have already stayed for one night inside the chiller.

13. I read somewhere that you should not combine morning pump and evening pump because the breast milk characteristic is different (evening one has more melatonine and thus sleep-inducing). Is this true?

I don't know.

But to be honest, I feel that this is too cumbersome, because that also means if you feed the wrong milk (say morning milk in evening feeding), you will get trouble.

Really?

I've combine all pumped milk throughout the day and my baby didn't have serious sleeping problem.

14. I've even read that you should not combine milk from left breast and right breast to avoid foremilk-hindmilk imbalance, is this true?

Well..., I would go crazy if I can't mix the pumped milk from left and right breast.

That's just too much work!

And I haven't read a good, trusted literature about it.

Usually it's from 'that nurse', or 'that mom' saying that.

Mix them, mamas.

Your baby would be okay. Mine is!

PS: If you do find a trusted literature about this, do let me know.

Kellymom has a great hand-out about breast milk storage and handling. You can check it out here.

That's it!

I hope this post is can give you clearer idea about how to freeze breast milk properly.

If you feel that this article helpful, do let me know.

I may expand it to include how to transport / store breast milk in workplace and how to thaw / prepare the milk for feeding.

::

Now, onto you.

Are there other questions that you have regarding how to freeze breast milk? No question is too silly to ask, just ask away!

Or do you have any tips / hacks about breast milk storage and handling to make it easier?

Feel free to share it in the comments.

Further reading: How To Rotate Your Breast Milk Stash