How to Safely Store Your Pumped or Expressed Breast Milk

Everything you need to know about how to ensure safe and correct storage for your breast milk.

By Sophia Smith

As a first-time mom, building up a stock of breast milk has been a saviour in so many situations. 

On nights when I desperately needed extra sleep, it allowed my partner to take overnight feeds. When heading out for a long overdue dinner with friends, I could rest assured that my baby was well-fed. When I considered my return to work, I had enough milk stashed to ensure that my baby would always get the best possible nutrition. 

Creating a stock of your expressed or pumped breast milk is a fantastic way to ensure your baby gets all the benefits of your liquid gold when you’re not around. However, storing your milk correctly is crucial for retaining nutrients, maximizing immunological benefits, and preserving its antioxidant qualities. 

That’s why I’ve put together this guide on how to ensure safe & correct storage of your liquid gold. 

What should I store my expressed or pumped breast milk in? 

Many moms use breast milk bags for storing their milk. These are specially designed to prevent leaks and are more durable than other types of plastic storage bags. Typically, they’re also printed with a space to write your baby’s name, the date & time of storage, and the quantity of milk. All important info for when you’re building up your stock! 

To avoid potential toxins when using plastic breast milk storage containers, it’s recommended to use containers that are not made with Bisphenol-A (BPA) - a potential endocrine disruptor. Certain types of plastic can even destroy essential nutrients in your milk, so it’s always best to stick to containers or bags which are specifically for human milk. 

Some mothers choose to avoid plastics altogether. Instead, they opt for storing in freezer-safe glass bottles. In this case, always make sure that lids are well-fitting and can be sealed tightly. And before storing your milk in glass bottles, they should be washed in hot, soapy water, and air dried before use.

It’s worth noting that ALL milk should be dated and labelled before storage. If you’re sending your baby to a nursery or daycare, labelling with their name is a must. 

How can I safely store my breast milk? 

There are three main ways to store your breast milk; keep it at room temperature (for quick use), refrigerate it, or freeze it. 

Storing your breast milk at room temperature: 

Expressed or pumped milk stays fresh for approximately 4 hours at room temperature (around 77℉ or 22℃). So although there’s no rush to give it straight to your baby, there is a time window to be taken into consideration. It’s also important to note that on hotter days, storage times at room temp will be shorter. 

Refrigerating your breast milk: 

Fresh milk can be kept in the refrigerator for 4-5 days. During this time, you can combine milk from several pumping sessions in the same container, so long as the newly expressed milk is cooled before adding it to your existing batch. 

Freezing your breast milk: 

Breast Milk stored in the freezer is good for around 6 months. According to the CDC, 12 months is also acceptable. However, many moms choose to do a “smell test” past the 6-month mark before serving to baby. 

With frozen milk, the rule is “first in, first out”! In other words - always use up your oldest milk first. 

Milk expands as it freezes - so be mindful not to fill containers right to the top if you plan on freezing. In fact, freezing in smaller quantities is often better for reducing milk waste, as babies typically drink between two to four ounces (60-120ml) in one feed. 

For optimal freezer storage when using milk bags, squeeze any air out from the bags and lay them flat.

Storage Locations & Temperatures
Type of Breast Milk Countertop / Room Temperature 77°F (25°C) or colder Refrigerator 40°F (4°C) Freezer 0°F (-18°C) or colder
Freshly Expressed or Pumped Up to 4 Hours Up to 4 Days Up to 6 months is best
Thawed, Previously Frozen 1–2 Hours Up to 1 Day (24 hours) NEVER refreeze human milk after it has been thawed
Leftover from a Feeding Use within 2 hours after the baby is finished feeding

Reheating Stored Milk 

Although breast milk can be served at room temperature or cold, many moms choose to heat it first. Here are some tips for warming your breast milk, depending on storage: 

Warming Refrigerated Milk: 

When reheating milk, remember this: go slow and low! By that we mean; slowly heat at a warm but not hot temperature. 

Never heat refrigerated milk directly on the stove. It gets too hot and this damages valuable nutrients. Microwaving is also advised against, as this can create “hot spots” in your milk which could burn your baby’s tongue. 

Instead, the best way to heat your milk is to immerse the container in a bowl of warm water, which will gradually and evenly heat it throughout. 

Thawing & Heating Frozen Milk: 

If you know ahead of time that you’ll need to thaw your frozen milk, the safest way to do so is by leaving it in the refrigerator overnight. Thawed milk can be kept in the refrigerator for up to 24 hours. 

Frozen milk can also be heated straight from the freezer in the same way as refrigerated milk; by gradually warming the container in a bowl or pan of warm water until totally thawed.

Can I reuse milk if my baby doesn’t finish it? 

Guidelines state that if you’ve already fed pumped or expressed milk to your baby, you have a window of 1-2 hours after the feed to give your baby the remainder of that milk. After this time, it should be discarded due to potential bacteria risks. Storing milk in smaller quantities is a great way to reduce wasting drops of your precious milk! 

Why does my milk look different after storing? 

This is totally normal! All milk, including breast milk, typically separates into two layers - the “cream” which floats to the top, and the milk at the bottom. 

You can give it a swirl around to combine the layers before you serve it to your baby, but DON’T shake the milk to mix it. This breaks up some of the long-chain fatty acids in your milk, which provide valuable nutrition to baby. 

What’s that smell coming from my stored milk? 

Some women find that after thawing their stored breast milk, it gives off a soapy smell or taste. This is down to having a high lipase content in their milk (the enzymes which break down fats). 

This milk is still safe for babies to drink. It’s possible to deactivate the lipase by heating freshly expressed milk until it bubbles at the edges (but NOT to boiling point), then quickly cooling and transferring to the freezer. 

Final Thoughts 

Ultimately, how you choose to store your milk is down to personal preference! Take into consideration your lifestyle, time constraints, and how often you plan to use your stored milk in order to make the right decision for you. 

Regardless of your chosen method - make sure you congratulate yourself, mama! Your efforts are ensuring that your baby continues to get all the incredible benefits of your liquid gold. 


La Leche League International. (2010) The Womanly Art of Breastfeeding (8th ed.) 

Academy of Breastfeeding Medicine. (2017) Clinical Protocol Number #8: Human Milk Storage Information for Home Use for Healthy Full Term Infants. Breastfeeding Medicine, 12(7), 390-395.

Lawrence, R.A. & Lawrence, R.M. (2010). Breastfeeding: A Guide for the Medical Profession (7th ed.). Elsevier Mosby, Philadelphia 

Center for Disease Control and Prevention (CDC) (2022). Proper Storage and Preparation of Breast Milk.

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