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Breastmilk Storage 101

Updated: Jan 24

Electric pump containers filled with milk and a stack of breastmilk storage bags.

Milk expression, or pumping, is common for most modern mothers. More women are returning to the workplace after having a baby, with maternity leaves ending sooner than they are ready to wean. Some families choose to exclusively pump and feed their babies with bottles because it is a better fit for them. Finally, sometimes mothers need to be away from their baby for a few hours or days due to appointments, travel, family obligations, care of other kids, etc. The reason for milk expression is unique for every family and doesn’t matter or change the recommendations. What is important though is to make sure the expressed milk is stored and used safely.

The CDC is a great resource for how to properly store and use expressed breast milk and serves as the reference for IBCLCs internationally. Here is their basic chart for proper storage:

Type of Breastmilk

Countertop/Room Temperature



Freshly Expressed/Pumped

Up to 4 hours

Up to 4 days

Within 6 months

(12 mos if deep freezer)

Thawed, Previously Frozen

1-2 hours

Up to 1 day

NEVER refreeze!

This can be printed from their website for your use, or Modern Guide to Breastfeeding has fridge magnets (you get one for taking the intro class or can message me to purchase).

Here are the basics of the breast milk storage chart and some tips on how to properly use the milk: 

  • Freshly expressed/pumped milk should be used or stored within 4 hours. 

  • If milk is in the fridge (cold), use it within 4 days. You can reheat it if the baby prefers warm/body-temperature milk.

  • If milk is frozen, it is good for 6 months. Make sure to label it, and don’t place it in the freezer door, since opening and closing the door would cause temperature changes regularly.

  • Frozen milk that has been thawed can be in the fridge for 24 hours. Frozen milk that has been thawed outside of the fridge or warmed for baby should be used within 1-2 hours. Milk that has started to thaw should never be re-frozen.

  • Once the baby has started to consume milk, the milk in that bottle should be used within 2 hours. Partially consumed milk beyond that 2 hour window should be discarded and cannot be put back in the fridge or re-frozen. 

  • If you have expressed milk at room temperature, it can be combined with milk that is also recently expressed or the same temperature (from the same day, within the safe 4 hours).

  • If you have milk in the refrigerator that is cold, it can be combined with other cold milk, again typically from the same day. Just make sure to only combine milk of the same temperature.

What containers are best for breastmilk storage? 

There are a lot of products on the market for this! Generally, any clean, dry, leak-free container will work - typically plastic, metal, or glass. Many mothers use milk storage bags. These can be especially useful in the freezer if you stack them flat. Just make sure to label the date you expressed the milk and place the bags in a clean Tupperware or bowl when thawing to ensure no leaked milk is lost. Some moms use a pitcher or mason jars in the fridge and combine milk at the same temperature from the same day. If you are on the go or at work, a product like the ceres chill can be extremely useful (again, there are a lot of options on the market). It helps to keep the milk at whatever temperature you may need and is convenient, especially with chilled milk, as it can replace a cooler or ice packs.

How do I heat the breastmilk back up?

Heating milk - whether from cold or frozen - should always be done carefully. NEVER microwave breast milk or bottles. Bottle warmers can be a useful alternative. Most have settings for the quantity of milk and the milk’s starting temperature. Using a warm water bath is also fine. Breast milk is most commonly served at body temperature (coming out of a breast) so many babies prefer it to be warmed. Always check the milk temperature before serving (most people will tap out a drop on their inner forearm to check). If your baby does not mind cold breastmilk that is fine, warming is not a requirement. And lucky you! Because nothing is worse than waiting on the bottle warmer at 2 am with a hangry little one. 

If there is concern ever about whether milk is good or if it has not been properly stored, it can still be fine to use it, just don’t consume it! Breastmilk is also great for nipple healing or milk baths for rashy, eczema-prone baby skin. 

Hopefully, this article will give you confidence in knowing how to safely store and use expressed breast milk. If you do have further questions, never hesitate to reach out to me or another IBCLC. Breastfeeding and expressing breast milk is a true labor of love. Every drop of milk is hard-earned and having to toss out milk can be devastating, so make sure you are using proper guidance in your breastmilk storage! 

*** These recommendations apply to healthy, full-term babies. If you have a baby in the NICU or with medical complications, you would want to discuss with an IBCLC or someone on your child’s healthcare team about what is best for them. 

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