How Long Does Breast Milk Last After Warming?

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We’ve all had those moments. We’ve prepared the milk for our little bundle of joy, and before they even have a mouthful, they’re out for the count. This used to stress me out! I would worry about whether my breast milk would stay fresh until my baby woke up.

I spent many hours researching so that I can bring you the answer here today! The burning question for me was, how long does breast milk last after warming? 

Let’s have a quick look at the right ways to warm breast milk, and then get into how long it lasts. 

How to Warm Up Breast Milk 

Yes—there’s a right way and a wrong way to do this! It’s important that you avoid overheating breast milk. Excessive heat can damage the unique enzymes found in mom’s breast milk, which reduces the great benefits it has on your baby’s immune system. 

The ideal temperature for warmed-up breast milk is 98.6 degrees Fahrenheit—right around body temperature. It’s worth noting that there’s no harm in feeding your little one cold milk! But most babies are going to be more comfortable taking in milk that’s slightly warm. 

I’ve found that the following methods are very efficient when warming up breast milk: 

Water Bath 

There are two methods you can use when it comes to making a water bath. The first is to warm water on the stove or get the water warm from the faucet. Fill a bowl with the warm water and place the sealed bottle of breast milk into the water. Leave the milk for a few minutes while it reaches the required temperature. 

You’ll need to check the temperature of the bottle, not the water. If the water cools down too quickly, the bottle won’t warm efficiently. You could also hold the bottle under warm running water, rotating the bottle to warm the milk up evenly. While this method works fairly well, it does waste water! 

Once the bottle has reached the right temperature, swirl it gently to incorporate the fat, which can sometimes separate while the bottle is standing.

Bottle Warmer 

Before you run out and buy a bottle warmer, do some research—not all bottle warmers are created equal. Some of them are designed to keep formula warm and aren’t suitable for breast milk. With that in mind, though, a bottle warmer can come in very handy to warm milk quickly for your baby in the early hours of the morning. 

Be sure to test the settings of the bottle warmer so that the milk isn’t overheated. I recommend a dry run before trying this in the middle of the night!

Travel Warmer

There will be times that you don’t have access to a bowl or running water. In these cases, a travel warmer is super handy. Just run it under hot water before you leave the house, and it will work like a thermos flask. It will not only warm the milk, but it will keep it toasty for a while. 

Hot Tip: Never warm your breast milk in the microwave! It heats unevenly and leaves hot spots that could burn your baby. 

How Long Does Breast Milk Last After Warming? 

Breast milk should be used within two hours of being warmed. If it’s one of those occasions where baby falls asleep before their bottle is warm, you should not reheat the milk when they wake up. Double-heated milk loses much of its nutritional value. 

If your baby does drink but doesn’t finish the milk, whatever remains should be discarded. As soon as your baby begins to feed, their saliva will start to break down the enzymes of the milk, so whatever remains is compromised. 

How Long Does It Last Once Expressed? 

  • You can store freshly expressed milk for up to four hours at room temperature. 
  • If refrigerated, fresh milk will last for up to four days. 
  • You can freeze freshly pumped milk for up to six months. 

Benefits of Choosing Breast Milk Over Formula 

One of the biggest challenges new mothers face is whether to breastfeed their child or to use formula. 

It may not be possible for all women to breastfeed, while others may choose not to breastfeed due to medical conditions or their comfort level. Thankfully, infant formula offers a healthy alternative in those cases. But there are some special advantages to using breast milk instead of formula. 

The American Academy of Pediatrics (AAP) recommends breastfeeding as it helps to build babies’ immunity. They also encourage mothers to breastfeed solely for the first six months and up until the 12-month mark with other food. 

It’s important to note that you can still feed your baby breast milk without actively breastfeeding! Simply use a breast pump to collect the milk. 

Benefits of breast milk include: 

  • It contains antibodies that help defend your baby against bacteria and viruses. 
  • It’s healthier for the baby’s tummy and causes fewer upsets. 
  • Breast milk contains hormones that promote and regulate appetite. 
  • Fatty acids in breast milk help develop baby’s brain and eyes. 
  • Stem cells in the milk support and repair organs. 

Tips and Tools to Keep Breast Milk Fresher For Longer 

Believe me; I know that every drop of breast milk counts! After doing my own research on how to save as much milk as possible healthily and safely, I’ve put these tips together:

  • Only store breast milk in containers intended for it—no plastic bags or disposable bottle liners. 
  • If you’re not sure you’ll use your milk within four days, freeze it immediately. 
  • Freeze milk in small batches! You can calculate roughly how many ounces you use per feed. 
  • Write the date on your containers, so you know exactly when it needs to be thrown away. 
  • Store milk on the refrigerator shelf and not in the door, to prevent temperature fluctuations when the refrigerator is opened!
baby bottle

How Can I Tell If Breast Milk Isn’t Good?

Unlike other types of milk, it can be hard to tell if your breast milk is spoiled. While giving most milk types a sniff will tell you if it’s off, you can’t really do the sniff test with breast milk. There are a number of things that can change the smell of your breast milk, and that doesn’t necessarily mean that it’s gone bad. 

Some things that can cause the smell of breast milk to change include: 

  • Certain medications. 
  • Food flavors. 
  • Storage containers. 
  • The freezing process. 

These factors can also affect the taste and the smell of the breast milk. Foods with strong flavors or even really spicy food can cause some seriously strange aromas! 

Generally, it’s nothing to be worried about, although I wouldn’t recommend feeding your baby spicy milk. What I’ve discovered is that there’s a range of “normal” when it comes to breast milk. 

The color range of breast milk can be off-white, slightly orange, yellow, and sometimes even pink. This can vary within the same expressing session, which has the potential to cause some confusion and slight panic! One of the reasons for this is due to the milk being more watery (foremilk) or thicker and more fatty (hindmilk). You’ll also notice that breast milk changes over the course of the day. 

If you notice these differences in your breast milk, there’s no need to stress. It doesn’t mean that the milk is bad. Doing a few more tests can let you know if it’s good to feed your baby. 

There are three ways to tell if your breast milk is spoilt:

  • Examine it: Milk naturally separates during expression, and you’ll see water on the bottom with the fat remaining at the top. When you give it a swirl, it should mix easily again. If your milk remains separate after swirling it or you see chunks floating in it, then it’s probably gone bad. It’s a good idea to get rid of it.
  • Taste test:  If you have a high lipase, the milk may take on a slightly sour taste. This is still safe, though! But there are degrees of sourness. If you taste the milk and it’s putrid, then it’s probably not healthy. It’s also good to taste test frequently so that you’ll be able to determine if your milk is on the sour side naturally. Frequent tasting also helps you spot differences faster.
  • The sniff test: As I’ve mentioned, this is not the most reliable test. If used in conjunction with the two tests above, though, it can offer some insight. The sniff test will be more reliable for milk that has been stored at room temperature or in the refrigerator.

When freezing milk that has a high lipase content, this could lead to it smelling sour when thawed. This milk would still be perfectly safe to use, though, if it passes the other tests. The best way for you to be sure is to freeze a small amount of milk for four to five days, thaw it and see what the scent it has after it has been frozen. 

Important Things to Remember:

Be mindful of the room temperature. Breast milk should be kept at 77 degrees Fahrenheit or less. Freshly expressed milk can be left on the counter for up to four hours before it needs to be refrigerated or frozen. 

Once the milk has been thawed, it can be left on a countertop for two hours before you should throw it away. You also cannot freeze breast milk again once it has been thawed! Any milk that’s leftover in the bottle after feeding your baby should be used within two hours. 

This can be overwhelming for new moms, I know! Although there’s a lot of info out there, if you remember just these few points, you and your baby will be fine:

  • Breast milk will last for about two hours after heating. 
  • Never reuse previously heated breast milk. 
  • Always label your breast milk with the date it was expressed. 
  • Refrigerated breast milk should be used within four days. 
  • Frozen breast milk can be stored for up to a year, but for safety’s sake, I recommend storing it for six months max! 


So, how long does breast milk last after warming? Stick to the two hour rule to be safe. 

There are a number of things that’ll cause your heart to skip a beat when it comes to your baby! Feeding them breast milk shouldn’t be one of them. 

Your baby will benefit from the nutrients they receive, and as long as you make sure to keep your milk fresh, there’s nothing to worry about!

Cristin is a co-founder of Smart Parent Advice, and the loving mother of two wonderful children. In her free time, she can often be found in a yoga studio or catching up on her favorite shows.