How much breast milk should you freeze

Q: Is it worth freezing 1 oz of breastmilk?

According to the Academy of Breastfeeding Medicine the ability to inhibit bacterial growth is lessened, especially by 24 hours after thawing”. So how much milk should you freeze? Anywhere from 1 to 4 ounces is appropriate.

How to Freeze and Unfreeze Breast Milk Safely

Find out how to properly store and use frozen breast milk.

Table of Contents Show

How to Freeze and Unfreeze Breast Milk Safely
Find out how to properly store and use frozen breast milk.
How to Thaw Breast Milk:
Here are some helpful guidelines for storing your breast milk safely.
The Rule of 4's
Where We Stand:
About Dr. DiMaggio:
How many ounces of breastmilk should I freeze together?
How much breastmilk do I need frozen?
Is it worth freezing 1 oz of breastmilk?

Photo: Monthira/Shutterstock

Producing more breast milk than your baby needs is a great problem to have. In my experience as a physician, most breastfeeding moms worry about producing too little milk, especially when they start pumping in addition to nursing, so that's why you've more than likely received the advice to never throw out your breast milk, but freeze it instead.

According to the Centers for Disease Control and Prevention (CDC), freshly expressed breast milk can be only safely stored in the refrigerator at 40 degrees F (4 degrees C) for 4 days. However, fresh breast milk can be stored in the freezer at 0 degrees F (-18 degrees C) or colder safely for 6 to 12 months.

Here's how to freeze and unfreeze breast milk safely:

After pumping, immediately pour the milk into breast milk storage bags or clean food-grade containers with tight fitting lids made of glass or plastic. Leave an inch at the top of the container because milk expands when it freezes.
Store your breast milk in smaller portions (2 to 4 ounces in a bottle/bag) so it will freeze and thaw faster.
Label every storage container with the date of breast milk collection. If you will be delivering breast milk to a childcare provider, clearly label the container with the child’s name and talk to your childcare provider about other requirements they might have for labeling and storing breast milk.
Place the bottles/bags in the freezer immediately. Store the milk in the back of the freezer (not in the door), where it's the coldest, and don't remove it until you're ready to thaw it and serve it to your baby.
Use the oldest milk first or discard it if you won't be using it safely in the future. If you've got plenty already in your freezer and you're still able to pump and store more, don't feel bad about discarding the oldest milk in your freezer.

Breast milk can be stored in an insulated cooler bag with frozen ice packs for up to 24 hours when you are traveling. Once you arrive at your destination, milk should be used right away, stored in the refrigerator, or frozen.

How to Thaw Breast Milk:

If you don't need the milk right away, simply move it to the refrigerator, where it will take 24 hours to thaw. Warm the milk by running warm water over the bag or bottle of milk and use it within the next 24 hours.
If you need it immediately, remove it from the freezer and run warm water over it until it's at room temperature.
Once you've thawed breast milk, don't refreeze it.
Do not thaw or heat it in the microwave. You run the risk of overheating the milk, which can harm your baby and destroy the milk's enzymes and immune properties.

By: Dina DiMaggio, MD, FAAP

When it comes to breast milk, how you store it depends on how soon you want to use it.

Here are some helpful guidelines for storing your breast milk safely.

Before expressing or pumping: Wash your hands and all storage containers thoroughly. Label the date the breast milk was expressed on each container and include your child's name if you are giving the milk to a child care provider. Talk with your child care provider about how they require breast milk be stored and labeled.
Store breast milk in small batches. 2 to 4 ounces is recommended to prevent waste. Any remaining breast milk left in a bottle after your baby is finished with a feeding should be used within 2 hours, or, if quickly refrigerated, used for the next feeding. You can always thaw an extra container if needed.
Refrigerate or chill milk right after it is expressed. Freshly expressed milk can remain at room temperature (up to 77°F or 25°C) for 4 hours (or up to 6 to 8 hours if very cleanly expressed), but it is best to chill as soon as possible.
Breast milk can be placed in the back of the refrigerator (39°F or 4°C). It is best to use refrigerated breast milk within 4 days, but it can be refrigerated for up to 8 days.
To warm breast milk from the refrigerator: Place the bottle in a bowl of warm water or run it under warm water. Microwaving breast milk is not safe due to the risk of scalding your baby with hot milk.
Freeze breast milk if you will not be using it within 24 hours. Breast milk expands as it freezes, so do not fill the milk all the way to the top of the storage container. Again store the milk in the back of the freezer, not the door.

If freezing the milk inside a refrigerator with a freezer that has a separate door (0°F or −18°C), milk may be frozen for up to 9 months.
If the freezer is a chest or a deep freezer (−4°F or −20°C), milk may be frozen for up to 12 months.

To thaw breast milk from the freezer: Put the bottle or bag in the refrigerator overnight, hold it under warm running water, or set it in a container of warm water. Remember that heating breast milk in microwaves is not safe.
Once breast milk is thawed: It can be stored in a refrigerator and must be used within 24 hours.

The Rule of 4's

We know breast milk storage can be confusing, so here is a more conservative approach that you can also go by (and easily remember): 4 hours at room temperature and 4 days in the refrigerator!

Editor's Note: Although these breast milk storage guidelines are appropriate for babies born premature and those who are hospitalized, hospitals may have their own rules. If you have specific questions, discuss these guidelines with your baby's pediatrician and/or hospital.

Where We Stand:

The American Academy of Pediatrics recommends breastfeeding as the sole source of nutrition for your baby for about 6 months. When you add solid foods to your baby's diet, continue breastfeeding until at least 12 months. You can continue to breastfeed after 12 months if you and your baby desire.

Additional Information & Resources:

Expressing Breastmilk On the Job
Breastfeeding and the Use of Human Milk (AAP Policy Statement)
Effects of Extended Freezer Storage on the Integrity of Human Milk (The Journal of Pediatrics)

About Dr. DiMaggio:

Dina DiMaggio, MD, FAAP, is a board certified pediatrician at Pediatric Associates of NYC and at NYU Langone Medical Center. She is the co-author of The Pediatrician's Guide to Feeding Babies and Toddlers, a comprehensive manual written by a team of medical, nutrition, and culinary experts. Follow her on Instagram @Pediatriciansguide.

The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.

How many ounces of breastmilk should I freeze together?

To avoid waste, store milk in small portions by putting only 60 to 120 ml (two to four ounces) of milk in the container (that's the amount your baby is likely to eat in a single feeding). Fill the container up to 3/4 only. Milk will expand when freezing. Squeeze out the air at the top of the milk bag before sealing.

How much breastmilk do I need frozen?

The amount of breastmilk you should aim to freeze before returning to work is anywhere from 27 to 70 ounces.

Is it worth freezing 1 oz of breastmilk?

According to the Academy of Breastfeeding Medicine the “ability to inhibit bacterial growth is lessened, especially by 24 hours after thawing”. So how much milk should you freeze? Anywhere from 1 to 4 ounces is appropriate.