Guide to Thawing and Defrosting Frozen Breast Milk

Posted by Jane Springston on

Freezing breast milk is a common practice of pumping mamas as a way of building up a “stash” to use at a later date. During maternity leave, I pumped at least once per day in addition to breastfeeding so that I would have plenty of extra breast milk when I headed back to work. Being able to pull out a bag of frozen milk is also really convenient for a date night or whenever you might be away from your little one. But before you give it to your baby, you’ll want to make sure that you are thawing it the right way. 

Not only do you want to follow safe practices when defrosting frozen breast milk, but chances are you want to get it done as quickly as possible. We’ve had a lot of practice with this here at the Baby’s Brew, so read on to find out exactly what we recommend. 

Ways to Safely Thaw Breast Milk From Frozen

There are multiple ways to thaw out frozen breast milk to get it into a liquid state. Each of the following can be done in a safe manner. Read each method carefully to find out how to do it correctly and which one will work best in certain situations. 

1.) In the Refrigerator

One of the easiest ways to defrost breast milk is by putting the bag or bottle of frozen breast milk into the fridge. However, this method takes planning. It takes about 12 hours for frozen breast milk to thaw in the fridge (give or take as it depends on how much you have). If you have a planned outing this is a great way to thaw breast milk as long as you’re on the ball! Just be sure to use the breast milk within 24 hours once it’s been thawed in the refrigerator (24 hours after no ice crystals are present.)

2.) In a Bowl of Cold Water

Though this method isn’t one you’d likely choose typically, it is one way to go if you need to milk faster than in 12 hours and know you won’t be able to use all of the milk you’re thawing. As long as the milk stays cold, you can refrigerate the unused portion that doesn’t go into your baby’s bottle.

3.) In a Bowl of Warm Water

This method is two-fold in that it will thaw frozen breast milk and warm it at the same time (if left in a bit longer). The trick is to replace the water that has gotten cold with more warm water. This will allow the breast milk to warm up more quickly. This method can be used with both breast milk storage bags and bottles, but the warming process will happen more quickly with bags.

4.) Under Warm Running Water

The fastest way to thaw your baby’s breast milk is under warm running water. This works particularly well if the breast milk is in a bag. As the milk starts to defrost, you can massage the bag to break up ice chunks in order to get it thawed more quickly. Ideally you’ll start with cool water and work up to running it under warm (not hot) water. 

5.) With a Bottle Warmer 

Though there are some bottle warmers that have the capability to warm breast milk from frozen, you want to take care that the warming method utilizes a slow-heat method that will safely warm breast milk without destroying any of its helpful properties. The better option is to thaw using one of the methods recommended above and then use your preferred bottle warmer. 

Our favorite bottle warmer is the world’s first battery-operated bottle warmer from the Baby’s Brew. Once milk is thawed, you can choose between 2 safe warming temperatures for breast milk and get your baby’s milk ready for feeding even when on the go. 

Need to travel with breast milk? Find out how to safely transport breast milk in, “How to Travel with Breast Milk by Car or “How to Travel with Breast Milk by Plane.”

Breast Milk Defrosting Practices to Avoid

As a busy parent, it can be tempting to take the “easy way” or “faster way” when thawing your baby’s breast milk, but these aren’t always safe methods.

1.) Don’t Thaw at Room Temperature

As a living fluid, breast milk should never be thawed at room temperature. In order to keep the healthy composition of the breast milk intact, including its antibodies and vital nutrients, as well as keep it from growing unhealthy bacteria, breast milk should never be left out on a counter, etc. to thaw.

2.) Don’t Use the Microwave

As we wrote about in our article, “Microwaving Breast Milk: Why it’s a No Go,” there isn’t ever a time that it’s safe to put breast milk in the microwave. Not only does this method create hot spots in the milk, putting your baby at risk for burns, but it also destroys the nutrients in the breast milk. There is no reason you need to use the microwave for thawing or warming. 

Other Tips for Freezing and Thawing Breast Milk

Thawing frozen breast milk is a pretty easy endeavor once you get the hang of it. After doing it a handful of times, you’ll know which method works best depending on what type of situation you are in. On top of finding the right thawing method, there are some other tips we recommend to give your baby the best experience taking breast milk from a bottle.

  • Store your baby’s milk in breast milk storage bags for faster thawing. Be sure to use bags made specifically for breast milk - these will be less likely to tear or puncture.
  • Freeze your baby's milk in small portions. This will help minimize wasted milk. Some parents even recommend freezing breast milk in ice cube trays so they are available in one-ounce portions.
  • When freezing in bags, lay them flat. This method will allow you to store more milk in as little amount of space as possible.
  • Always thaw and give your baby the oldest milk first. You may hear this method referred to as, “First in, first out.” This is why you’ll see breast milk storage bags with a place for you to write the date in the permanent marker. Though the guideline is to use frozen breast milk within 6 months, as discussed in our breast milk storage and handling article, it’s better used up in closer to four months. By using the oldest milk first, you’ll likely be able to avoid coming close to the milk’s expiration date.
  • After thawing, swirl the milk before giving it to your baby. Human milk will separate during storage, so swirling or stirring it will get it back to the proper composition.
  • Warm milk with a bottle warmer if it’s been thawed in the refrigerator. Though babies CAN drink milk cold that’s taken straight from the refrigerator, many babies won’t. We recommend taking the chill off by warming it first - either in a bowl of warm water or with a bottle warmer that uses slow-heat technology safe for warming milk, such as the Baby’s Brew
  • If thawing a bag of breastmilk in a bowl of warm water, place it inside a ziploc bag. Leaks can happen with breastmilk storage bags, so this will make sure you don’t lose any of your precious liquid gold.
  • Don’t fear if the milk smells a little different than you’d expect. Breast milk that’s been refrigerated or frozen may have an excess of the enzyme lipase which can change the smell and taste of breast milk, according to Kelly Mom

Thawing Frozen Breast Milk FAQ

Below are some of the most commonly asked questions about defrosting breast milk.

Q: How long does it take to thaw breast milk?

A: These are the approximate times it takes to thaw frozen breast milk:

  • In the refrigerator - about 12 hours
  • In a bowl of warm water - about 20 minutes
  • Under warm running water - 5 - 10 minutes

Q: How long does breast milk stay good after thawing?

A: Breast milk needs to be given to your baby within 24 hours after a complete thaw in the fridge (so 24 hours after all ice crystals are gone). If it has been warmed at all (such as thawing in a bowl of warm water) it needs to be consumed within 2 hours.

Q: What is the fastest way to defrost frozen breast milk?

A: The fastest way to defrost frozen breast milk is by holding it under a tap of running warm water. It will go even faster if it’s in a breast milk storage bag instead of a bottle.

Q: Can I refreeze thawed breast milk?

A: Unfortunately, it is not safe to refreeze breast milk that has already been thawed from a frozen state. If you are unable to give the milk to your baby within 24 hours after it’s completely thawed in the refrigerator, it should be thrown out because, according to La Leche League, this practice “may introduce further breakdown of nutrients and increases the risk of bacterial growth.”


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