Collecting & Storing Breastmilk

November 29, 2011

Storing breastmilk is a great option no matter if you’re returning to work, exclusively pumping, or just looking to give other family members an opportunity to feed your little one. The benefits of breastfeeding are extensive, however it’s important that nursing mothers understand breastmilk storage guidelines and safe handling instructions before they get started. So, use the information below as reference when giving your baby the best nutrition possible.

Breastmilk Storage Guidelines:

  • Room Temperature: 4 to 6 hours
  • Cooler with 3 Ice Packs: 24 hours
  • Medela Cooler Bag with Ice Pack: 12 hours
  • Refrigerator: 3 to 8 days
  • Deep Upright Freezer: 6 to 12 months
  • Freezer Compartment of Refrigerator (separate doors): 3 to 6 months
  • Freezer Compartment of Refrigerator (one door): 2 weeks
  • Thawed Breastmilk: 24 hours (Do not refreeze)

Safe Handling Instructions for Collecting and Storing Breastmilk:

  • Store breastmilk in clean, BPA-free containers intended for breastmilk storage.
  • It is normal for stored milk separates into layers with the cream at the top.  Gently swirl warmed bottles to mix the milk layers. Don’t shake.
  • You can continue to add small amounts of cooled breastmilk to the same refrigerated container throughout the day.  Avoid adding warm milk to already cooled milk.
  • Pumped milk may be added to frozen milk provided it is first chilled and the quantity is less than what is frozen.
  • Store your milk in collection bottles or in disposable bags specifically designed for breastmilk. Avoid using plastic bottle inserts.
  • Freeze milk in 2 to 5 ounce portions.  Small amounts will thaw more quickly.  You will also waste less milk this way and avoid over-feeding.  Liquids expand when frozen so be sure to leave some extra room at the top of the container so the bottle or bag won’t burst.
  • Seal containers tightly.  Write the date on a piece of tape on the bag or bottle.  You can also use Medela’s Labeling Lids for convenient organization.
  • Sometimes defrosted breastmilk can have a soapy taste or odor.  This is due to a normally occurring enzyme, lipase, which helps to digest the fat content of the breastmilk.  To avoid this from occurring, scald the breastmilk (do not bring to a boil) on a stove until tiny bubbles appear along the sides of the pan; do this before it is frozen.  The scalding process will neutralize the enzyme preventing the soapy taste or smell.
  • Never microwave breastmilk.  It causes hot spots that can burn your little one’s mouth.  Microwaving can also change the composition of breastmilk.
  • Thaw milk overnight in the refrigerator, or hold the bottle under warm running water to quickly thaw.  You can also place the sealed container in a bowl of warm water for 20 minutes to bring it to body temperature.

Note: These guidelines may differ if your baby was born premature. Check with your healthcare provider for specific breastmilk guidelines for premature babies.

Looking for a breastmilk storage guidelines quick reference? You can download the chart below by clicking here.












Do you have any tips for breastmilk collection and storage? Share them in the comments below.

29 thoughts on “Collecting & Storing Breastmilk

  1. Pingback: Already a mommy? Questions about freezing breast milk - Page 2 - BabyandBump

    • Hi Izzy’s Mom,

      I’m sorry that you’re having trouble with your storage bags leaking. Customer Service would be happy to help you find a solution, please call 1-800-435-8316 for assistance.

      Thank you,

    • Hi Kiki,

      Yes, you can run warm water over a storage bag to quickly thaw. You can also place a sealed bag in a bowl of warm water for 20 minutes to bring it to body temperature.

      Hope this helps!

  2. Hi,

    I want to freeze my expressed milk laying flat to save room. But I’ve heard that during the thawing process, the bag can leak. Has this been a problem with the medela bag. Do you recommend to freeze upright or flat with your type of bag? Please advice. Thank you.

    • Hi Quinn,

      As long as your bags are sealed tightly, it shouldn’t matter whether they are frozen upright or flat. Make sure you’re not overfilling your bags, as this can cause them to expand when frozen and leaks may occur. If you have further questions, please call Customer Service at 1-800-435-8316.

  3. I left my breast milk in my pump last night that had already been chilled in the fridge. It was not in the cooler pack. Do I have to throw it away now.

    • Hi Rachel,

      While freshly-expressed milk can be stored at room temperature for 4-6 hours, you may want to discard milk that has been previously chilled and thawed. It may be safe to use, but it depends on how long it was left out – and milk that has gone bad will have a distinct smell and taste. Here is more information on reusing expressed milk, including if you leave milk out at room temperature: Please also feel free to contact our Lactation Consultant for one-on-one advice via email here: Hope this helps!

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