How to Defrost Breast Milk Safely | Baby Brezza
Skip to Content
Early Access July 4th Sale up to 40% OFF | FREE Shipping & Returns

Defrosting Breast milk: How to Thaw Frozen Breast Milk the Safe Way

So you’ve been storing your breast milk in the freezer and are now ready to use that liquid gold that’s been hiding behind the ice cream. Defrosting breast milk correctly is essential. Improper thawing can negatively affect the nutritional properties of the milk and make it unsafe for your baby. What are the safe ways to thaw frozen breast milk, and what methods should you avoid? Whether you’re defrosting breast milk in hot water or thawing breast milk in a bottle warmer, here’s a breakdown of the best options out there to ensure your little one is receiving as many nutrients as possible.



Sometimes, the best frozen breast milk warmer isn’t warm at all– let us explain. It takes approximately 12 hours to defrost breast milk in the refrigerator. If you know your little one will need milk in the morning, move it from the freezer to your fridge in the evening and let it thaw overnight. This helps ensure that no nutrients are lost in the warming process and can help parents bring the milk to the right temp from a more controlled starting point– rather than going straight from frozen to warm.

If you’re trying to learn how to defrost breast milk bags or bottles for the first time, keep temperature control in mind. Defrosting breast milk in hot water correctly is all about knowing how “hot” you’re allowed to make the water in question. Hold a bag or bottle of frozen breast milk under warm running water. Start at a lower temperature and gradually increase the heat to a maximum of 99 degrees F.


Similar to defrosting breast milk under warm running water, parents can also consider thawing their frozen liquid gold in a bowl of warm water. Simply find a bowl big enough to fit the bag or other container of breast milk, fill it with water no hotter than 99 degrees F, and set the frozen milk inside, rotating when necessary. After a few minutes, your defrosted breast milk should be ready for feeding time! 


Thawing breast milk in a bottle warmer all depends on the equipment available. Bottle warmers can defrost breast milk, but traditional bottle warmers use only steam heat, which is too hot and can destroy those all-important breast milk proteins. Look for a bottle warmer that will preserve milk nutrients– and choose one that has a designated setting for becoming the ideal frozen breast milk warmer. An excellent option is the Baby Brezza Safe + Smart Baby Bottle Warmer. It’s the only warmer with two settings -- one for breast milk and another for formula -- to ensure both are safely heated to the right temperature. 

Defrosting breast milk doesn’t have to be a guessing game. For breast milk, the Steady Warm setting uses a warm water bath (instead of steam) to safely defrost breast milk. The warming basket fits most milk storage bags, plus you’ll never have to worry about overheating thanks to its auto shut-off.

For formula, the Quick Warm setting uses steam heat to rapidly and safely warm formula and baby food. Even better -- it’s the only smart warmer, so you can operate it from your phone with Bluetooth using the FREE Baby Brezza app and get alerts when your bottle is ready.

For moms who are not particularly tech-savvy or just don’t want the added Bluetooth function, we introduce the Baby Brezza Bottle & Breastmilk Warmer. Get the same settings and intuitive design at a more affordable price, and thaw breast milk in a bottle warmer the better, safer way.



To defrost breast milk bags the right way, always avoid the microwave. Defrosting breast the milk in the microwave can cause the milk to get too hot, which can destroy nutrients and spoil the milk. There’s also a chance the milk will heat unevenly, creating dangerous “hot spots” which could scald your baby’s mouth.


Like we mentioned earlier, defrosting breast milk in hot water is a slippery slope: too hot, and those important nutrients– as well as your little one– could be at risk. Using boiling water to thaw frozen breast milk will have a similar effect as microwaving it. The milk will lose beneficial antibodies, and there is a risk of creating heat pockets. 


Whether you’re thawing breast milk in a bottle warmer or with one of the other safe methods we’ve mentioned, there are a few time factors to keep in mind. Once thawed, breast milk can be refrigerated for up to 24 hours. If kept at room temperature, it should be used within two hours or thrown away. Stanford Children’s Health has other guidelines for thawing and using frozen breast milk.

Can You Defrost Breast Milk & Put It Back in the Refrigerator?

Once you thaw breast milk in a bottle warmer, parents have a small window of time to work with it, whether they go ahead and use it for feeding time or store it for a little longer. After using a frozen breast milk warmer, you can use the milk immediately, leave it out (at room temp) for a maximum of 4 hours, or store it in the refrigerator for another 24 hours.

Can I Mix Breast Milk from Two Different Days?

When learning how to thaw breast milk properly, there are a few extra guidelines to keep in mind, such as blending milk from different days. Once you thaw breast milk in a bottle warmer, it is highly advised to keep batches separate– meaning parents should not blend milk from different days. While a frozen breast milk bag warmer makes warming convenient, blending and reheating milk together from different days runs the risk of rewarming old nutrients that shouldn’t be combined with a fresh batch, ruining them both.

Can Babies Drink Cold Breast Milk?

Babies can absolutely drink cold breast milk, as the temperature does not have an effect on breast milk’s nutritional composition. However, most babies tend to take to warm breast milk or formula more easily due to it replicating natural warmth from the body. This is why thawing breast milk in a bottle warmer is useful: it takes less time to thaw, and your bottles are ready for feeding time with perfectly warm milk.

Baby Feeding & Formula Prep

← Older Post Newer Post →

Save 15%
on your first order of $50+

Be the first to know about new products and special offers