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Feeding & Scheduling

Written by The Twin Source


How long can breast milk be left out? How long will frozen breast milk last? What’s the best way to thaw frozen breast milk? We’ve got those answers and more.


Breast Milk Storage

Follow the rule of 5:

  • Breast milk can be left out at room temperature for 5 hours before being refrigerated.
  • Breast milk can be refrigerated for 5 days before being frozen.
  • Breast milk will last for 5 months in a standard freezer.


The rule of 5 tends to be the most conservative and easiest way to remember guidelines for breast milk storage. While most lactation consultants and breast-feeding resources follow and recommend these rules, there is no real research to back them up.


Breast Milk Tips

  • Do not re-freeze defrosted breast milk.
  • Pumped breast milk from different pumping sessions in one 24-hour period can be combined if they are both cooled to the same temperature.
  • Do not add freshly frozen milk to a bag of frozen breast milk, since it could defrost the frozen breast milk.
  • Refrigerate breast milk before freezing.
  • Thaw frozen breast milk by transferring it to the refrigerator, time permitting, or by placing it in a bowl of warm water.
  • Avoid using the microwave oven to thaw or heat bottles of breast milk since microwaves do not heat liquid evenly and excess heat can destroy the nutrients in breast milk.
  • Previously frozen milk that has been thawed in the refrigerator must be used within 24 hours.
  • Freeze breast milk in small portions (2 to 5 ounces) so it’s easier to thaw.
  • Always leave extra room at the top of breast milk storage bags so the bag won’t burst.
  • Sometimes babies do not finish bottles of breast milk. Check with your doctor about re-refrigerating and re-using this milk.


Always remember, the information contained on The Twin Source is not intended for medical diagnosis. Any medical information found on this site should be discussed with your health care professional. Always consult your doctor for any medical advice.

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