Thawing, Warming, and Using Frozen Breast Milk

Safety Guidelines for Defrosting Human Milk

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Many breastfeeding mothers collect and freeze their breast milk. Sometimes they need to transport or ship it, but most moms freeze their milk to create a stockpile to have on hand when they stop breastfeeding. So, what do you when you're ready to defrost all that stored milk? Here's a guide to safely thawing, warming, and using your frozen breast milk.

Tips for Safely Thawing Breast Milk

Thawed breast milk is milk that has been frozen and defrosted. When you thaw your breast milk according to the safety guidelines, it maintains more of its nutrients, and it's less likely to spoil. Here are some tips for safely thawing your breast milk:

  • Your frozen breast milk should be dated. Defrost the oldest container of breast milk first.
  • You can defrost your 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 breast milk at room temperature.
  • Do not use the microwave or place your breast milk in a pot of boiling water on the stove. The breast milk may get too hot, and it can spoil.
  • Once your breast milk is defrosted (but not yet warmed up or used) you can warm and use it immediately, leave it out at room temperature for up to four hours, or place it in the refrigerator for up to 24 hours.

Note: 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 for more information on how to collect, store, and use your breast milk.

Thawing 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.

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. Thawing breast milk in a bowl of warm water 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. Start out with cold running water and slowly make the water warmer. Keep the water warm, but not hot. 

The Dangers of Using the Microwave and Stove

You should not use a microwave oven to thaw or warm frozen breast milk. The high heat from the microwave can destroy some of the healthy properties found in the breast milk. Microwaves also cause uneven heating and hot areas in the milk. Hot spots in the breast milk can burn your baby's mouth and throat. Heating breast milk on the stove is not recommended, either. It's easier to overheat breast milk when you place it in a pot of boiling water on the stove. Overheating can destroy the nutrients in the milk and make it dangerously hot for your child.

The Taste of Defrosted Breast Milk 

Sometimes defrosted breast milk has an unpleasant smell or a soapy, metallic taste. That doesn't mean the milk has gone bad, and you don't have to throw it away. It is the result of an enzyme in the milk called lipase that naturally breaks down fats during storage. It's still safe to give to your baby, but your child may not like the taste of defrosted breast milk and could reject it.

Warming Up Thawed Breast Milk 

You can give your baby thawed breast milk directly from the refrigerator, or you can warm it up to room temperature or body temperature. 

  • If you choose to warm your breast milk, you can do so by placing it in a bowl of warm water for a few minutes, holding it under warm running water, or using a bottle warmer. As mentioned above, you should not heat breast milk in the microwave, or in a boiling pot of 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.  
  • During storage, breast milk separates into layers. Once you defrost and warm your breast milk, you can gently swirl or shake the container to mix the layers before feeding it to your baby.
  • Always check the temperature of the breast 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 Safe Handling of Warmed or Used Breast Milk

To prevent spoiling and the growth of bacteria in your breast milk, follow these guidelines:

  • Once breast milk is warmed up, you can give it to your child right away or put it in the refrigerator for up to 4 hours. You should not leave warmed breast milk out at room temperature. 
  • If you warm breast milk, do not refreeze it. 
  • If your baby does not finish a feeding, you should throw away the leftover breast milk in the bottle.  
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Article Sources
  • Academy of Breastfeeding Medicine Protocol Committee. ABM Clinical Protocol# 8: Human Milk Storage Information for Home Use for Full-Term Infants. Original protocol March 2004; revision# 1 March 2010. Breastfeeding Medicine. 2010;5(3).
  • Eidelman AI, Schanler RJ, Johnston M, Landers S, Noble L, Szucs K, Viehmann L. Breastfeeding and the Use of Human Milk. Pediatrics. 2012 Mar 1;129(3):e827-41.
  • Lawrence, Ruth A., MD, Lawrence, Robert M., MD.  Breastfeeding a Guide For The Medical Profession Eighth Edition. Elsevier Health Sciences. 2015.
  • Riordan, J., and Wambach, K. Breastfeeding and Human Lactation Fourth Edition. Jones and Bartlett Learning. 2014.