Guide to Storing Breastmilk in Mason Jars

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If you have followed me for a minute, you know sustainable living is my jam. I was raised in a home where we were careful about avoiding waste, and the 3 R’s, (reduce, reuse, recycle). Sustainability is the fancy term for the continual well-being of the environment, economy, and society. I love how in the last decade or so more and more companies have become sustainably conscientious. An example of sustainable living is shopping for clothes at Goodwill (see my thrifting post here) is a sustainable choice because it keeps clothes out of landfills (environmental), provides jobs to people with disabilities (social), and saves up to 50% off, if not more than the item's original price (economical).

Storing breastmilk in mason jars offers a blend of practicality and sustainability, making them an excellent choice for preserving the nutrition and quality of your baby's milk. In this blog post, I am going to show you how to store your precious breastmilk for your perfect little one! 

I have committed to breastfeeding our twin babies for a year. Breastfeeding is such a special way to bond with my babies (I also tandem feed!) and I love all the health benefits that comes along with breastfeeding. I pump for three reasons: one to help maintain my supply, two to help express milk when I am engorged, and three to have milk on hand for when a babysitter is watching our babies. I store my breastmilk in 4oz Mason jars in the fridge and freezer. I love the 4oz size because they easily stack on each other, and they do not take up a lot of space in the fridge. The great thing about the size of these jars is that they are small so they can thaw quickly.

I remember in my babysitting days, I worked at an in-home daycare for a mom who was breastfeeding. She used plastic breastmilk storage bags to store breastmilk in the freezer. I did not like the bags because they weren’t the easiest to transfer into bottles and they leaked.

Upon finding out I was pregnant, I began researching ALL the things of course, and one of them being if breastmilk could be stored in glass jars. I did not want to have to keep buying pricey storage breastmilk freezer bags that I could only use one time. I already had 4oz Mason jars, so I wanted to use them to store my breastmilk, and then eventually use them for baby food. Ball mason jars are my favorite brand of glass jars, but other glass jars can work too! Mason Bottle offers milk + food storage for babies too. 

Here are some tips on building your freezer supply:

My favorite tip - lactation cookies!! Oh these are so delicious. My FAVORITE recipe is from Say Grace's blog. You can find her recipe here. Honestly, they don't taste like a lactation cookie, they taste like an amazing chocolatey dessert! 

Here I am mixing lactation cookie dough while holding the babies in their Weego carrier

Drink water. This is an obvious one, but so easy to forget/prioritize, at least for me. According to WebMD, while breastfeeding, you should be drinking 128 ounces (16 cups) of water a day.

Eat watermelon. My father-in-law surprised me by buying a watermelon, and when I cut into it, it was yellow on the inside! I had never heard or seen golden watermelons before! They taste exactly like a traditional watermelon. It was a small watermelon, and I ate the whole thing - it was so refreshing. The next morning when I pumped, I pumped over 4.5oz on each side!

I cut into the watermelon to find it was yellow! I was so surprised! 

Any content provided by my blog, Merry Madden is in my opinion and is not intended to replace medical advice from a healthcare provider.


-Have to make sure they are completely flat when freezing

-Hard to add more milk into

-Can leak 

-Only use once 

-Can only be used for breastmilk 


-Can be used for other purposes (I am going to use these for baby food once the twins are 6 months old!)

-Multiple uses


-Easily stackable

-Easily add more milk


  • Amazon sells smooth-sided 4oz mason jars, but the “quilted” kind will also work, however, I prefer smooth-sided jars to easily see how much milk I have in each jar.
  • Ball also has leak-proof lids which are dishwasher safe, and they will not rust.
  • Use Haaka or breast pump to express breastmilk.
  • Sterilize both the lids and jars either in the dishwasher or in a baby bottle sterilizer (I used Phillip’s sterilizer during our babies’ first three months).
  • Label the top of the lids with the date and the time. Keep breastmilk in the fridge for up to 4 days, and then if not used, transfer to the freezer for up to 6 months. 


Labeling breastmilk: To make life simpler, instead of writing the exact time it is, I round down to the nearest hour. This way I am giving myself an extra buffer when it comes to the freshness of my milk. For example, if I finished pumping at 12:37pm, I write 12pm on the label. 

I use reusable labels that can be erased with either a magic eraser or any eraser. These reusable labels are dishwasher and freezer-safe safe. However I have noticed our dishwasher will cause the labels to come off, so I just wash the lids by hand. 

If you want to know exactly how much milk is in each jar, you can use a food scale to find out the amount of ounces in each jar. First place a clean, empty jar on the food scale, and make sure to set it to tare. Then add in breastmilk to the jar, and the scale will only show how much milk is in the jar. I bought my Taylor scale in 2021, and it is a kitchen staple for me!

Best of luck mama! Breastfeeding and pumping is no easy task. I hope this article is helpful to you and your little one. 


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