bamama is reader-supported. When you buy through links on our site, we may earn an affiliate commission. Learn more

How Long Does Breast Milk Last After Warming [Explained!]

How Long Does Breast Milk Last After Warming [Explained!]

Producing milk to breastfeed their babies is one of the MOST FULFILLING parts of a new mother’s journey. However, it takes a lot of effort and energy, and it’s no wonder moms want to utilize every drop for their children. 

Thus comes the question: How long does breast milk last after warming? 

I first heard this query when my cousin started pumping milk for her firstborn. She wanted to ensure her stash won’t be put to waste, especially since her supply was limited and she was preparing to return to work. 

Fortunately, after asking her mom’s advice and doing research, she discovered the answer, and I thought it was worth sharing with you!

So if you have the same concern, don’t worry! I’ll try to answer this question briefly in this article. 

How Long Does Breast Milk Last After Warming?

The benefits of breastfeeding and breast milk aren’t a mystery. Most moms are already aware, which is why they choose to express and store breast milk for their baby to consume rather than settle for milk formula. 

Some parents even buy breast milk from other moms and stash it in their freezers. This makes it easier to access nutritious breast milk when your little one gets hungry. Any member of the household can warm it up and serve it.

But before freezing and warming breast milk becomes part of your everyday routine, it’s best to understand how long breast milk last

According to the Academy of Breastfeeding Medicine, breast and formula milk thawed to room temperature must be used within 2 hours.  But if you defrost it without bringing it to room temperature, the milk can last 24 hours

A warm environment is a good breeding ground for bacteria. Hence, following this two and 24-hour window is vital to ensure your little ones won’t get sick from consuming expired milk

There are also instances wherein the milk gets soiled even before the recommended number of hours lapse. So before feeding your baby, it’s important to check if your breast milk shows signs of expiration to avoid getting them sick. 

Signs that Warmed Breast Milk Has Gone Bad

Signs that Warmed Breast Milk Has Gone Bad

There are several ways to identify if the milk has already gone bad. Three of these include:

  • Foul/rotten smell – you’ll immediately notice a pungent odor coming from your baby’s bottle or storage bag once the milk expires. Whether it forces your gag reflex or not, don’t feed it to your baby if it doesn’t smell right.
  • No swirl – the fat will naturally separate into the upper and lower regions of the storage bag if fresh breast milk is left undisturbed. But with a slight shake or swirl, all its contents will effortlessly mix together. However, if you notice chunks of curd that don’t reintegrate into the milk in one swirl, it’s already expired and unsafe for consumption. 
  • Musty taste – if the milk doesn’t taste like milk at all or leaves traces of sourness contrary to its natural taste, it’s safe to conclude that it can no longer be used to feed your baby. 

Proper Breast Milk Storage

Proper Breast Milk Storage

Proper storage is one of the significant factors in keeping the freshness of breast milk. Hence, practicing this as you start your milk-pumping journey is essential. 

Here are a few tips I can give you when storing breast milk:

  • Use airtight containers – it’s always best to keep baby bottles and storage bags sealed and airtight to avoid contamination and water penetration. In turn, it will keep the milk from getting soiled quickly.
  • Use insulated storage when traveling – when you’re bound to go on long trips, storing the milk in well-insulated soft or hard coolers filled with ice is best. This keeps the milk cold to extend its longevity to the following day. Once you arrive at your destination, use the milk immediately, freeze it, or place it in the fridge.
  • Keep 4-ounce portions – as mentioned, once you already warmed the milk to room temperature, you need to use it immediately. Hence, to avoid wasting your precious milk, keep it in smaller portions, just enough to feed your baby in one go. 
  • Freeze at -18 degrees or cooler – after expressing the breast milk, place it in the freezer to let it freeze at -18 degrees Celsius or cooler. This will allow the breast milk to last for 6 to 9 months. Also, make sure to keep your freezer clean, as well as the breast pump and other equipment used when expressing milk. 

How to Warm a Baby’s Bottle

How to Warm a Baby’s Bottle

Most of the time, when my cousin’s away, I am the one-call-away tita tasked with caring for the kids. 

When it was my first time caring for my pamangkin, a few months old at the time, my aunt and cousin taught me the right way of warming their milk. 

In case you also need a guide on how to properly warm your baby’s bottle, I provided some tips here to follow:

  • Keep the milk in airtight bottles – as previously mentioned, it’s best if we keep their milk in airtight containers to avoid contamination and keep the milk fresh for longer. 
  • Don’t make it too hot – ensuring the milk doesn’t get too hot keeps the essential nutrients from breaking down. It also keeps the baby from burning their tongue as you try to feed them. You must avoid directly heating your baby’s bottle or storage bags in boiling water or the microwave. The best way to do it is placing warm water in a bowl or mug before putting the bottle in. You can also defrost it under running tap water or lukewarm water until it reaches the desired room temperature. 
  • Mix it well – once you reach the right temperature for the milk, take it out and mix it well. This allows the heat to distribute properly and balances the spread of milk fats to avoid hot spots. 
  • Test the temperature – it’s always important to test the milk’s temperature before feeding it to your little one. Pop off a few drops onto your wrist or the back of your hand, and see if the warmness is tolerable, especially for a baby. Note that babies are more sensitive, so what’s warm for you might be a few times hotter for them. 

Frequently Asked Questions (FAQs)

Now that you already know the facts related to how long breast milk is good for before being discarded, you’re all set and ready to go!

But in case you still have more questions, I answered some frequently asked questions in this section.

Can I Reheat My Baby’s Bottle?

Yes, but only within the 2-hour window

As mentioned, it’s recommended that once your baby’s bottle is already warmed, you can only leave it at room temperature for 2 hours.

The next time you feed your baby, you can either leave it as is or reheat their baby bottle

Can I Put Breast Milk Back in the Fridge After Warming?

Yes, you can put it in the fridge after warming. But given that it was already warmed and has reached room temperature, you need to use it within the next 2 hours.

On the other hand, after completely thawing frozen milk, you can put it back in the fridge as long as it hasn’t been set to room temperature. 

Putting it back in the fridge will SLOW DOWN bacteria’s growth. But you still need to feed it to your baby within 24 hours to avoid it going bad. 

Can I Mix Breast Milk Expressed from Different Days?

Generally, it’s okay to mix breast milk from different days. However, it will affect the shelf-life of your freshly pumped milk when mixed with old batches. 

You must follow the shelf-life of the first milk added to the storage bag. Doing otherwise would cause your breast milk to soil and make it unsafe to feed to your little one. 

Hence, while it’s generally okay to do so, I suggest storing milk expressed from different days separately to ensure you’re giving your baby good milk every feeding time. 


Now that you know the answer to your breast milk query, it’s time to start following the 2-hour window for warmed milk at room temperature and the 24-hour window for refrigerated milk

Plus, observe the signs of soiled milk before feeding your baby. 

No matter how much is left in that storage bag, if time has already lapsed, it’s best to discard the milk before it makes your baby sick. 

Additionally, to avoid wasting your precious liquid gold, it’s best to store it in small portions, enough for your baby’s recommended dose every feeding time. 

Sky Bustillo
Sky Bustillo

Hi, I’m Sky!
As a Filipina in her mid-20s, a sister to young ones, and a tita to my nieces and nephews, I somehow share the same sentiment as other parents. I have a growing aspiration of becoming a mom someday!
But there also comes a worry that you won’t be able to give the best to your children, especially with the food they eat, the products they use, and the new habits and hobbies we introduce to them.
Your kid’s safety and welfare are your top priority, that’s why I always make it to a point to learn from the stories and experiences of other moms.
It’s a delight to share what I learned and know to help the moms close to my heart, and this time, I’m writing to relay advice to you from the insights of other moms and my experience around kids, too.
I’d love to be a part of your journey, and I hope you find these tips and tricks helpful for you and your young one!