How to warm up breast milk

OK mama, now that you’ve mastered the art of pumping, and you’ve saved up a sweet little freezer stash, it’s time to put that milk (and hopefully your partner) to work. We know you, and your boobs, have worked hard for that liquid gold, so we’ve put together this handy guide on all you need to know about how to warm up breast milk, so you don’t have to stress about wasting a single precious drop. Let’s dive in.

First up: do you need to warm up breast milk

The short answer: You don’t! Babies can safely drink cold breast milk—helpful to know if you’re in a pinch with no way of warming your bottle up.

Deciding whether to use warmed breast milk or not really comes down to what your baby prefers. Though it’s worth noting that when breast milk is stored in the fridge or the freezer, the fat tends to separate, and warming it up can help bring back the normal consistency.

How to warm up breast milk: step by step

If you’re wondering how to properly warm up breast milk, there are a few different ways. At the end of the day, it comes down to choosing the method that works best for you. 

How to warm breast milk from the fridge

  1. Warm-up a bowl of water, either on the stove, in the microwave or using a kettle, until it’s warm (note—not boiling!) 
  2. Place the tightly sealed bag or bottle of breast milk in the bowl of warm water. You could also run it directly under warm water from your tap.
  3. Leave the milk under the tap or in the bowl for five or so minutes, until it reaches body temperature. 
  4. Swirl the milk to mix in the fat (don’t shake it—you don’t want it to froth!)
  5. Test the temperature of the breast milk (more on how to do this later.)

How to warm frozen breast milk

Defrost it in the fridge then follow these same steps (if you need your frozen milk ASAP, you can also defrost breast milk in warm water but be prepared for it to take 15 minutes or even longer.) 

Warming breast milk: commonly asked questions

How can you check the temperature of breast milk after warming?

We can’t stress enough that you should always test the temp of your breast milk before giving it to your baby. 

Place a few drops of breast milk on the inside of your wrist—it should feel slightly warm, the same as your body temperature. If you’re feeling fancy, you can also use an instant-read thermometer. And, FYI—putting your finger in the breast milk or placing it on your lips is not the best idea, as your germs can get into the milk. 

Can you warm breast milk in the microwave?

This is a big no! Microwaves don’t heat evenly, so they can create hot spots that can burn your bub. Plus, using a microwave may also damage the nutrients and antibodies in your precious liquid gold. However, microwaves are OK for heating the water used to warm your breast milk. 

Can you warm breast milk on the stovetop?

You can use the stovetop to warm up a bottle breast milk, in a pot of water, though we don’t recommend it. Heating the bottle over constant heat makes it damn tricky to not overheat the milk, and plastic bottles might even start to warp, or leach harmful chemicals into your breast milk. Eek! Our advice? If you need to use the stove, just heat the water and then transfer into a bowl before using it to heat your bottle.

Do you need a bottle warmer?

A bottle warmer is a clever device that will do all the hard work for you, by warming your breast milk to the perfect temp every time. Is it necessary? Nope. Is it a bloody godsend for 3am feeds? We’re going to say yes. 

How long can you let breast milk sit out?

Freshly expressed breast milk can sit out for up to four hours before you need to pop it in the fridge. When it comes to breast milk that’s been warmed, you’ve only got up to two hours on the clock to get that milk into that baby, mama. 

Tip: While it’s sitting out, keep your breast milk covered so no bacteria can sneak its way in. 

Can you reuse previously heated breast milk?

We know how precious your breast milk is, but if you’re wondering, can I warm breast milk twice? We’re sorry to say that the answer is no. Reheating destroys the good bacteria and nutrients, plus, bacteria from your baby’s mouth could contaminate it. We know, we know, every drop is precious, but it just ain’t worth the risk. And yes, sadly this also means you can’t put warmed breast milk back in the fridge to use another time. 

Can you overheat breast milk?

Yup! Just like anything, you can overheat breast milk, which is why you need to be careful and always test the temp before feeding your baby. Overheating will not only burn your baby’s little mouth, but it also takes away the essential nutrients in your boobie juice. 

Does warming up breast milk change it?

Turns out you’re not seeing things—your breast milk probably will look a little different after being warmed up. The colour may take on a slightly yellowish, blueish or brown tinge, but it still has all the same nutrients and taste. 

How do you know if breast milk has gone bad?

If you want a simple way to know how long warm breast milk is good for, check for curdling (if it doesn’t mix back together), an unusual smell or a sour taste (if you are willing to go that far.) Or, save yourself and play it safe by chucking it out.

Can you add cold breast milk to warm breast milk?

You can add cold breast milk to warm breast milk while you’re using it, but don’t add freshly expressed, warm breast milk to a bottle of cold milk already in the fridge—you may end up reheating the cold milk. Instead, let the warm milk cool in a separate bottle or bag, and then combine once both are at the same cooler temperature. 

There is a lot of info out there about warming breast milk, but try not to stress out—feeding babies is hard work, so no matter how you decide to go about it, what you know or still need to learn, you’re doing great. 

Read next: How to increase breast milk supply

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