How to Store, Freeze, and Defrost Breast Milk

Some people express breast milk and store it to use later. You can refrigerate it if you plan to use it quickly, but if you need to store it for longer, you’ll likely keep it in the freezer. Not everyone needs to do this, but it can be handy even if you just need an occasional night out. But then you might like to know how to use it when you need it.

How Long Does Breast Milk Last?

Safe breastmilk storage guidelines are pretty simple. You can keep freshly pumped or expressed milk:

• Out on the counter at room temperature for up to four hours
• In the refrigerator for up to four days
• And if you freeze it, you can keep using it for up to a year!

It’s important to remember that those guidelines are for FRESHLY expressed milk. If you’ve been storing it, then take it out of the freezer or refrigerator, use some, and want to save the rest for later, it’s different. You don’t want to leave it out of refrigeration for more than two hours. If you put it back in the refrigerator, you’ll want to use it within 24 hours. And you never want to refreeze milk that’s already been thawed.

Following these guidelines is important because you worked hard for that milk! It can be very disheartening to leave milk out for too long then have to throw it away.

Why Thawed Breast Milk Might Smell Strange

Sometimes, milk that has been refrigerated or frozen can have a strange smell. If you’re thawing out some frozen breastmilk and notice this, don’t worry. As long as you’ve been following safe storage and handling guidelines, it’s most likely just high lipase milk. Some people describe the smell as metallic, soapy, or even fishy. This happens because the lower temperature of the refrigeration causes a natural change in the fatty acids. This actually helps prevent bacterial growth. It is safe to use, and babies usually don’t mind it.

What to Avoid When Thawing Breast Milk

It might not be something you would have put much thought into before, but what do you do when you’re ready to use the milk you’ve been storing? We take food out of the freezer all the time! Is breast milk the same? You might thaw breast milk the same way you thaw food, but there are a couple of very important differences to remember.

• DO NOT put breast milk in the microwave! This can cause uneven heating and possibly burns to your baby, and it can also damage some helpful components in the milk.
• DO NOT put the milk in a pot on the stove. It’s too hard to regulate the temperature this way and it might get too hot which can damage the milk or cause burns.

It’s also not the best idea to leave it out at room temperature to thaw. It might be fine if you’re watching it very closely, but if you leave it out too long, it can quickly become unsafe to drink.

Best Ways to Safely Thaw Breast Milk

Here are some better ideas for thawing breast milk:

• Put it in the refrigerator overnight. If you know you’ll need the milk tomorrow, put it in the fridge the night before. It should be thawed out by the time you need it, but it’s also still safely stored under refrigeration.
• Run warm water over the milk. Most people store milk in small quantities, so this method can be a quick and safe way to thaw it.
• Put the milk in a bowl of warm water. Just be sure not to leave it very long. It usually takes less than 5 minutes.
• BE CAREFUL WITH BOTTLE WARMERS! Some bottle warmers can be used to defrost breast milk, but not all of them have the correct setting for this purpose. You do not want to use high heat or a steam setting. That can damage the milk. Bottle warmers aren’t at all necessary for defrosting frozen breast milk, but if you have one, check for the defrost setting. That will work similarly to using a bowl of warm water to thaw the milk, with the added benefit of keeping the water at that temperature.

How to Handle and Feed Thawed Breast Milk

There are a lot of different methods for defrosting breast milk. You can choose what works best for you, but there are some general guidelines that are good to know regardless of how you do it.

• Use the oldest milk first. Put a date on the milk right after you express it. You might even store the containers in order. Keep the oldest ones near the front and put the new containers at the back of the line.
• Milk can be served warm, room temperature, or cold. Most babies don’t need the milk to be the perfect temperature.
• Stir or swirl, don’t shake. You’ll probably notice that the milk has separated during storage. You’ll see a thicker fat layer and a more liquid milk layer. You’ll want to mix those layers to avoid clogging bottle nipples and so the milk is a good balanced texture and flavor for your baby. If you shake it too vigorously, it might get frothy and harder to drink. There are also some claims that vigorous shaking can damage some helpful components of the milk (although I can’t find any good sources to prove that!).
• If you struggle to mix the milk completely and can still see the creamy film on your container, you can try warming the milk or bottle so it melts and blends in with the rest of the milk. You might even just be able to hold the bottle between your hands to get it warm enough to melt. Or you can put it in some warm water.

References:

Breast Milk Storage and Preparation | Breastfeeding | CDC

Storing and Thawing Breast Milk | WIC Breastfeeding Support