Pumping and Storing Frozen Breast Milk

Breast milk bottles with labels for days of the week

Verywell / Ellen Lindner

At some point during your breastfeeding experience, you may need to pump or express your breast milk. If you are not going to use it right away, you can store your milk to use in the future.

Reasons for Collecting and Freezing Breast Milk

Women express their breast milk for many reasons.

When you collect expressed breast milk correctly, you can freeze and store it for six months or even longer. You may choose to pump and freeze your breast milk if:

  • You are returning to work or school, but you would like your child to continue to receive your breast milk.
  • You need to relieve the pain and swelling of breast engorgement.
  • You want to create a supply of breast milk to use when you're no longer breastfeeding.
  • You want to slow down a forceful let-down reflex or a fast flow of breast milk.
  • You would like to provide your baby with breast milk when you cannot be with him or her.

How to Freeze Breast Milk

If you are pumping breast milk for a premature baby or donating to a milk bank, the collection and storage process may be more strict. Ask the hospital staff or the representative at the milk bank for the proper collection and storage guidelines to follow. 

The following are step-by-step instructions for collecting and freezing breast milk that you plan to use at home for your healthy, full-term baby.

  1. Choose your collection container. When you're planning to freeze your breast milk, be sure you choose a container that can withstand the freezing and thawing process. There are many different types of containers that can be used to store breast milk including breast milk storage bagsplastic bottles, glass containers, and breast milk trays. When you're selecting the container that's right for you, think about how long you plan to keep your breast milk in storage. Some breast milk storage bags, for example, are mainly designed for freezing and can be stored flat, and then stacked, which saves a lot of space. However, you should not choose regular plastic sandwich bags that can leak and break. Glass and hard plastic will give your breast milk the best protection if you plan to store your milk for a longer time. Whichever container you choose, it should be clean, BPA-free, and safe for the storage of food. Depending on the amount of breast milk that you're able to pump, you may need to have additional collection containers ready.
  2. Gather your supplies. If you are hand-expressing your breast milk, all you need is a clean collection container. If you are pumping, you should prepare your pump, pump flanges, tubing, and collection container(s). All of your pumping supplies should be clean and dry to prevent any bacteria from entering your breast milk as you pump.
  3. Label your breast milk container. Before you begin to express your breast milk into the storage bag or container, you should label it with the date and time of the collection.
  4. Wash your hands. Always wash your hands before you begin to pump, express, or handle your breast milk. Any germs on your skin can get into your breast milk as you're collecting it. The best way to prevent contamination is by keeping everything as clean as possible.
  5. Pump or hand express your breast milk. Use a breast pump or a hand expression technique to remove the breast milk from your breasts and place it into your breast milk storage container. If you use a breast pump, pump for about 10 minutes on each side. Hand expression takes approximately 20 to 30 minutes.
  6. Don't overfill your storage container. If you are using the same collection container to collect and store your breast milk, be sure not to fill it all the way to the top. Breast milk expands in the freezer, so it needs the extra room on the top. If you fill the container to the brim, it can burst. Therefore, you should stop adding breast milk to the container when it's approximately 2/3 or 3/4 full. If you still have more to pump, go on to a second container. If you are pouring your breast milk from the collection container into a different storage container, complete the collection of your breast milk then pour your milk into the storage containers. As instructed above, do not fill the storage containers to the top. Your breast milk needs that room to expand.
  7. Seal your storage container. Once you put the desired amount of breast milk into the container, seal it with the proper airtight zipper seal or cap. A bottle nipple cannot provide an airtight seal, so you shouldn't use a nipple when you're storing your bottles in the freezer.
  8. Freeze your breast milk. ​Place your breast milk into the freezer ​as soon as possible after you collect it. The recommendation is to store your milk toward the back of the freezer where it's typically the coldest. If you put your breast milk in the refrigerator first, freeze it within 24 hours. If a refrigerator or freezer is not available, you can put your milk in an insulated cooler with frozen ice packs for up to 24 hours and then freeze it.

How Long You Can Freeze Breast Milk

The type of freezer you have will determine how long you can store your frozen breast milk. 

  • 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 Freezer Compartment Within a Refrigerator: Breast milk can be stored in a freezer compartment inside a refrigerator for approximately two weeks.
  • A Stand Alone Freezer: Breast milk can be stored in a deep freezer without a defrost cycle for up to one year.

Freezing Breast Milk for Child Care

If your child goes to a babysitter or a daycare, ask about their breast milk policy. When labeling your breast milk with the date and time, don't forget to include your name and your baby's name.

Thawing Frozen Breast Milk

When it's time to use your frozen breast milk, follow the guidelines for the safe thawing and warming of breast milk. 

  • Check the dates and follow the guidelines for safe storage above. Thaw the oldest collection within the guidelines first.
  • Once frozen breast milk is thawed out, you should not refreeze it.
  • To safely thaw frozen breast milk you can place it in the refrigerator overnight. For a quicker thaw, you can place it in a container of warm water or hold it under warm running water. You should not thaw your breast milk at room temperature.
  • You can use defrosted breast milk right away or place it in the refrigerator for up to 24 hours.
  • You should not defrost or warm breast milk in the microwave or a pot of boiling water on the stove.
2 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. Department of Health and Human Services Office on Women's Health. Your guide to breastfeeding.

  2. CDC. Proper storage and preparation of breast milk.

Additional Reading

By Donna Murray, RN, BSN
Donna Murray, RN, BSN has a Bachelor of Science in Nursing from Rutgers University and is a current member of Sigma Theta Tau, the Honor Society of Nursing.