How to reheat breast milk from refrigerator

Many breastfeeding parents choose to collect and freeze breast milk. It might be necessary if you have to transport or ship it, but it is more likely that you want to create a stockpile to have on hand for when you have to be away from your baby or when you decide to stop breastfeeding. When the time comes, it's important to know how to safely thaw, warm, and use your frozen breast milk.

Thawing Frozen Breast Milk

When you thaw frozen breast milk according to safety guidelines, it maintains more nutrients and is less likely to spoil. Your bags or containers of frozen breast milk should have a label with a date. Use the oldest container of breast milk first.

Defrost frozen breast milk by placing it in the refrigerator, putting it in a bowl of warm water, or holding it under warm running tap water. You should not thaw frozen breast milk at room temperature.

Do not use the microwave or place your breast milk in a pot of boiling water on the stove. Once defrosted, you can warm up your breast milk and use it immediately, leave it out at room temperature for up to four hours, or refrigerate it again for up to 24 hours.

These guidelines are for healthy, full-term infants and older children. If you have a premature baby or a child with a compromised immune system, talk to your healthcare provider about how to collect, store, and use your breast milk.

Defrosting Breast Milk in the Refrigerator

Thawing breast milk in the refrigerator can take approximately 12 hours, so be sure to plan ahead. You may want to place a full day's worth of frozen breast milk in the fridge each night so that it will be ready to use the next day. To defrost frozen breast milk in the refrigerator:

1. Remove the bag or bottle of the frozen breast from the freezer.
2. Place it into the refrigerator.
3. Wait until the solid frozen milk turns back into liquid form.
4. Once the milk thaws, use it within 24 hours.
5. Do not refreeze thawed breast milk that is left over after 24 hours.

Thawing Breast Milk in a Bowl of Warm Water

If you need to thaw breast milk quickly, you can use a bowl of warm (not hot) water. This method takes approximately 20 minutes if you keep an eye on the water and change it as soon as it cools down. Here's how:

1. Fill a bowl or pan with warm water. 
2. Place the frozen container of breast milk into the water. Be sure to keep the water level below the cap of the breast milk bottle to prevent contamination.
3. As the water cools down, empty it and replace it with more warm water.
4. Continue to do this until the breast milk is no longer frozen.
5. Once defrosted, place the milk in the refrigerator or continue to warm it up to feed to your child. 

Thawing Breast Milk Under Running Water

The fastest way to defrost breast milk is to hold it under a faucet of warm running water. Here is what you can do:

1. Start out holding the container (or bag) under cold running water.
2. Slowly make the temperature of the running water warmer, but do not make it hot.
3. Keep holding the container under warm water until the milk thaws.

Sometimes thawed breast milk doesn't smell very good. It can also have a soapy, metallic taste. If this happens, it doesn't mean the milk is bad. The strange sour smell and taste are from an enzyme in the milk called lipase. Lipase naturally breaks down the fats in the milk during storage. It is still safe to give the milk to your baby, but your child may not drink it if they don't like the way it tastes.

Warming Up Thawed Breast Milk 

You can give your baby thawed breast milk right out of the refrigerator, or you can warm it up to room temperature or body temperature. If you choose to warm your breast milk, you can place it in a bowl of warm water for a few minutes, hold it under warm running water, or use a bottle warmer.

You should not heat breast milk in the microwave or in a pot of boiling water on the stove.​ ​It's important to warm your breast milk correctly so that you don't burn your baby's mouth and throat.  

Once the milk is warm, gently swirl the container to mix any layers that may become separated during storage. Check the temperature of the milk before giving it to your child. You can do this by squirting a few drops on the inside of your wrist. It should feel lukewarm or room temperature. It should not be hot or cold.

The Dangers of Using the Microwave and Stove

When thawing or warming a container or frozen milk, you should not use a microwave oven. The high heat from the microwave can destroy some of the healthy properties found in the breast milk. Microwaves can also heat in an uneven way, causing hot areas within the breast milk. These hot spots can burn your baby's mouth and throat.

Using the stove to heat breast milk is not recommended, either. When you place a bag or container of breast milk in a pot of boiling water on the stove, it can overheat. Overheating can destroy the nutrients in the milk and make it dangerously hot for your child.

How to Safely Handle Warmed Breast Milk

You can prevent your breast milk from spoiling or becoming a breeding ground for bacteria if you know how to handle it and use it safely. Here are some tips:

• Once you warm the breast milk, you can give it to your child right away or it can be refrigerated again for up to 24 hours.
• You should not leave warm breast milk out at room temperature. 
• You should not refreeze it.
• If your baby does not finish a feeding, you should throw away the leftover breast milk in the bottle.  

A Word From Verywell

Whether it's just a few bags in case of an emergency or a whole stockpile of containers for when you return to work, it nice to know that your child can still have your breast milk even when you're not available. How you thaw and use your frozen breast milk is as important as how you collect and store it. Follow the guidelines to keep your baby and your breast milk as safe and healthy as possible.

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. Centers for Disease Control and Prevention. Proper storage and preparation of breast milk. Updated January 22, 2020.

2. Eglash A, Simon L. ABM Clinical Protocol #8: Human milk storage information for home use for full-term infants, revised 2017. Breastfeed Med. 2017;12(7):390-395. doi:10.1089/bfm.2017.29047.aje

3. Bransburg-Zabary S, Virozub A, Mimouni FB. Human milk warming temperatures using a simulation of currently available storage and warming methods. PLoS ONE. 2015;10(6):e0128806. doi:10.1371/journal.pone.0128806

4. Ballard O, Morrow AL. Human milk composition: Nutrients and bioactive factors. Pediatr Clin North Am. 2013;60(1):49-74. doi:10.1016/j.pcl.2012.10.002

Additional Reading

• Breastfeeding and the use of human milk. Pediatrics. 2012;129(3):e827-41. doi:10.1542/peds.2011-3552

• Centers for Disease Control and Prevention. Breastfeeding and special circumstances. Updated December 22, 2019.

• Lawrence RA, Lawrence RM. Breastfeeding a Guide For The Medical Profession Eighth Edition. Elsevier Health Sciences, 2015.

• Riordan J, Wambach K. Breastfeeding and Human Lactation Fourth Edition. Jones and Bartlett Learning, 2014.

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.

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