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Storing Breast Milk

Topic Overview

The antioxidant and other protective properties of breast milk are most important and beneficial to your baby when breast milk is fresh. The protective components of breast milk decrease with refrigeration and freezing. But stored breast milk is the next best thing to fresh breast milk as a complete and nutritious food source for your baby.

Breast milk can be stored and then used in the following ways:

  • Kept at room temperature [ 15°C (59°F) to 20°C (68°F)] for no longer than 4 hours. If you’re not planning to feed your baby fresh breast milk within 4 hours after expressing it, refrigerate or freeze the breast milk right away.
  • Kept fresh in a cooler with an ice pack [ 15°C (59°F)] for 24 hours.
  • Stored fresh in the refrigerator [ 0°C (32°F)] to 4°C (39°F)] for up to 4 days (96 hours), unless your baby is in the neonatal intensive care unit (NICU) or the breast milk has additives. If your baby is in the NICU, fresh breast milk can be stored in the refrigerator for up to 3 days (72 hours). If the fresh breast milk has additives, it should be stored in the refrigerator for no more than 24 hours after the additives are mixed in.
  • Kept in the freezer compartment of a 1-door refrigerator [ temperature lower than 0°C (32°F)] for up to 2 weeks.
  • Kept in a refrigerator freezer with a separate door [ temperature lower than 0°C (32°F)] for up to 3 months.
  • Kept in a deep freezer or chest freezer [ -18°C (-0.4°F) to -20°C (-4°F)] for up to 12 months – or up to 6 months if your baby is in the NICU.

Safe storage tips

Follow these tips when you prepare breast milk for storage.

  • Be sure to wash your hands before pumping or handling milk that will be stored.
  • Food grade storage containers should be clean and dry. Wash them in hot soapy water or in the dishwasher. They do not need to be sterilized if your baby is more than 4 months old.
  • If your baby is younger than 4 months, sterilize storage containers by boiling them for 2 minutes or using your dishwasher’s sanitize cycle.
  • Breast milk storage bags, bottle liners, or small ziplock bags can be used for storage, held upright in cups if needed. Be sure the bags are sturdy and stored in a place where they will not get punctured or damaged. Avoid plastics made with bisphenol-A (BPA) (recycle symbol #7).
  • If you plan to freeze the milk, allow a little space at the top of the bag—the milk will expand when it freezes. It's also important to put the date the milk was expressed on the outside of the bag. The date will help you know which milk to use first and when to get rid of milk you didn't use.
  • Milk from both breasts expressed during the same session can be combined in one container. It is best to use a container that holds enough milk for one feeding. You are less likely to have to discard unused milk.
  • For the most consistent temperature control, store milk at the back of the refrigerator or freezer compartment.
  • Do not mix fresh expressed breast milk with cooled or frozen expressed breast milk. Instead, chill fresh breast milk for 1 hour in a refrigerator before adding it to a container with already cooled or frozen breast milk. Keep the original expressed breast milk date on the container if you add more breast milk to it on a different day.
  • Frozen breast milk will separate because the fat floats to the top. This separation is normal and does not mean that the milk has spoiled or is otherwise unusable. After thawing breast milk, shake the container gently and the fat will redistribute evenly.

Safe thawing and preparation tips

Follow these tips to prepare frozen or refrigerated breast milk.

  • To thaw frozen breast milk, run warm water over the storage container (which may be a bottle or a plastic bag) until the milk becomes slushy.
  • To warm breast milk, place the container in a pot of warm water on the stove for no more than 15 minutes. You can also use a milk warmer and follow the manufacturer’s instructions.
  • Do not cover the lid or nipple of the bottle or container with water when it’s being warmed. This can contaminate the breast milk.
  • After you have warmed the milk, gently shake the container to mix it. Test the breast milk on the inside of your wrist to make sure it’s not too warm to feed to your baby. It should feel lukewarm to the touch. Do not put the bottle nipple in your mouth to check the temperature or to clean it. This can pass germs to your baby.

Do not:

  • Refreeze thawed or warmed milk.
  • Use thawed (and then refrigerated) breast milk after 24 hours.
  • Use a microwave oven for warming milk. Microwaves heat unevenly, creating hot spots that can burn your baby's mouth and throat.

After feeding your baby, throw away any leftover breast milk after 1 hour at room temperature. Do not put it back in the refrigerator or save it for the next feed.



  1. Eglash A, et al. (2017). ABM Clinical Protocol #8: Human milk storage information for home use for full-term infants, revised 2017. Breastfeeding Medicine, 12(7): 390–395. Available online: Accessed February 1, 2018.


Adaptation Date: 9/21/2022

Adapted By: Alberta Health Services

Adaptation Reviewed By: Alberta Health Services

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