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How to Collect, Store, Freeze and Thaw Breast Milk


Updated May 30, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Formula in Baby Bottle
Alexandra Grablewski/Digital Vision/Getty Images

At some point during your breastfeeding experience you may need or want to express your breast milk. If you are not going to use the milk right away, you might want to store it. When properly collected and stored, expressed breast milk can be frozen for 6 months or even longer.

Reasons You May Express Your Breast Milk

  • To relieve engorgement.
  • To slow down a forceful milk ejection reflex or fast flow.
  • To provide breast milk to your baby when you are not with him or her.
  • You are returning to work.
  • You would like to create a supply of breast milk to use when you are no longer breastfeeding.

If you are expressing breast milk for a premature baby or to donate to a milk bank, the collection and storage process may be more strict. Follow the guidelines of the hospital or milk bank.

How to Collect Breast Milk to Be Frozen

  • Always wash your hands before expressing or handling breast milk.

  • Make sure your collection container is clean.

  • Use a glass container, BPA-free (Bisphenol A) plastic container, breast milk storage tray or plastic storage bag made specifically for breast milk collection. Do not use a regular plastic sandwich bag. It can leak or break during storage.

  • Use a breast pump or hand express your breast milk into the storage container.

  • Do not fill the container to the top. Stop adding milk when the container is 2/3 to 3/4 of the way full. Breast milk will expand when it is frozen so it will need room.

  • Seal the container with an airtight cap. Do not use a nipple from a baby bottle to seal your container.

  • Place the date on each container.

  • Freeze breast milk as soon as possible after collection.

  • Store the container at the back of the freezer where it is the coldest.

Types of Freezers

A Freezer Compartment Within a Refrigerator: Breast milk can be stored in a freezer compartment inside a refrigerator for approximately 1 month.

A Freezer Attached To a Refrigerator With Its Own Door: Breast milk can be stored in a standard Side by Side or Top and Bottom Refrigerator/Freezer Unit for up to 6 months.

A Stand Alone Freezer: Breast milk can be stored in a deep freezer without a defrost cycle for up to one year.

How to Thaw/Defrost Breast Milk

  • When you are ready to use your frozen breast milk, be sure to thaw it properly. You can thaw breast milk in the refrigerator, by placing it in a bowl of warm water, or by holding it under warm running tap water.
  • Thawing breast milk in the refrigerator can take several hours. Be sure to plan ahead of time. You may want to place frozen milk into the refrigerator at night for use the next day.
  • To thaw breast milk using a bowl of water, fill a bowl or pan with warm water and place the frozen container of breast milk into it. As the water cools down, empty the cool water and replace it with more warm water. Continue to do this until the breast milk is no longer frozen.
  • The fastest way to defrost breast milk is to hold it under a faucet of warm running water until the breast milk has thawed.
  • Never thaw frozen breast milk in the microwave. The high heat from a microwave can destroy some of the healthy properties found in the breast milk. Microwaves also cause uneven heating, so hot areas in the milk can burn your baby’s mouth and throat.
  • Do not place the breast milk in a pot of boiling water on the stove. The breast milk may get too hot and can spoil.

How to Use Thawed/Defrosted Breast Milk

  • Once thawed, warm the breast milk to room temperature or body temperature before giving it to your baby. You can warm the milk by placing it in a bowl of warm water for a few minutes, holding it under warm running water or using a bottle warmer. Do not warm breast milk in the microwave or by boiling it on the stove.
  • During storage, breast milk separates into layers. Once defrosted and warmed, gently shake or stir the container to mix the layers of milk before feeding it to your baby.
  • Check the temperature of the breast milk before feeding your baby by squirting a few drops on the inside of your wrist. It should not feel hot or cold.
  • Once thawed, breast milk can be used immediately or placed in the refrigerator for up to 24 hours.
  • Try to thaw only what you need because any remaining breast milk will have to be thrown out after 24 hours. Do not refreeze breast milk that has been thawed.
  • If your baby does not finish a feeding, throw away the remaining milk. Do not reuse any breast milk that is left over after a feeding.
  • Defrosted breast milk may have an unpleasant odor or a soapy, metallic taste. You do not have to throw the milk away, it has not gone bad. This is a natural occurrence as the fat in the breast milk breaks down. It is perfectly safe to give to your baby, however, your child may not like the taste of defrosted breast milk and could reject it.


American Academy of Pediatrics. New Mother’s Guide To Breastfeeding. Bantam Dell. New York. 2006.

Lawrence, Ruth A., MD, Lawrence, Robert M., MD. Breastfeeding A Guide For The Medical Profession. Mosby. Philadelphia. 1999.

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