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Storing Breast Milk


Collecting breast milk is a way of giving your baby breast milk in a bottle. If you collect milk, you can store it so you don't have to use it right away.

Why store breast milk?

Storing breast milk lets you feed your baby later or allows someone else to do it. This is useful if you're going back to work or will be gone at feeding time. It's also a way to give your baby breast milk if he or she can't breastfeed.

How long can you store breast milk?

Breast milk can be stored 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

Here are tips for storing breast milk safely.

  • Wash your hands before pumping or handling milk that will be stored.
  • 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 your baby is younger than 4 months, sterilize storage containers by boiling them for 2 minutes or using your dishwasher’s sanitize cycle.
  • Wash storage containers in hot, soapy water or in the dishwasher. They do not need to be sterilized if your baby is more than 4 months old.
  • 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.
  • Write the date that the milk was pumped on the outside of the bag or bottle.
  • 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.

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 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.


Adaptation Date: 2/12/2023

Adapted By: Alberta Health Services

Adaptation Reviewed By: Alberta Health Services

Adapted with permission from copyrighted materials from Healthwise, Incorporated (Healthwise). This information does not replace the advice of a doctor. Healthwise disclaims any warranty and is not responsible or liable for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.