How Long Can Breast Milk Sit Out Before Going Bad? Keep It Safe!

“Oh no!”, you tell yourself as you rush to that bottle of breast milk you forgot all about in the middle of whatever life threw at you that day, hoping and praying that it’s still good for your baby to drink and hasn’t gone bad yet.

After all, you went through all that work and put in all the effort you can to pump what little baby needs – the last thing you’ll ever want to happen is for all this effort to have gone to waste.

We know that a bottle of breast milk stored in the refrigerator can stay fresh and last for up to 5 days from storage, but the same is not nearly true for a bottle left outside, which will go bad in much less time.

Whether you’ve removed the milk bottle from the fridge and just forgot all about it outside, or you pumped, put it in a bottle, got distracted with something else that popped up on the spot and left it there for a long period of time, breast milk won’t last forever before it goes bad.

How Long Can Breast Milk Sit Out Before Going Bad?

There are several different answers to this question depending on the circumstances of breast milk we’re talking about, so here’s a list that covers all of those circumstances and gives an answer for every one.

Pay close attention so you know what to do if you ever find yourself in any of these circumstances, because after all, you definitely don’t want your baby to get sick because they’ve been fed breast milk that has gone bad!

Just Pumped

If you’ve just finished pumping (or were interrupted by something that made you pause and come back to it later), freshly pumped breast milk will last for different duration depending on where you left it last.

Freshly pumped milk can sit out for around 6 to 8 hours if left in a place where the temperature is between 60 to 85 degrees Fahrenheit (room temperature), while it will only last between 3 to 4 hours if left in a place where the temperature is higher than 85 degrees Fahrenheit.

With that being said, the Mayo Clinic advises that even if you freshly express breast milk into a bottle and store it in room temperature, that you don’t leave it outside for more than 4 hours before either storing it in a fridge or having your baby feed from it.

The higher the temperature is where the breast milk is stored, the faster the growth of harmful bacteria inside will be, which causes the milk to become harmful after a while.


If you reheated a bottle of breast milk and left it outside for a while, you’re not as lucky as the “just pumped” category of moms above.

Experts recommend that you don’t leave a reheated bottle of breast milk outside the fridge for more than one hour at most.

Thawed Milk

If you’re dealing with thawed milk, you can keep it in the refrigerator for up to 24 hours before it’s no longer suitable to give your baby to feed.

After these 24 hours have passed, the risk of harmful bacteria growth rises sky-high. And, if you’re keeping thawed milk outside for a while at room temperature, you only have around 2 hours on average before it goes bad.

An important note to also make is that you shouldn’t re-freeze thawed milk if it’s been frozen before.

Putting In The Fridge For The First Time

If you’re just refrigerating freshly pumped breast milk for the first time, you have 3 to 5 days on average before it goes bad and is no longer safe to give your baby.

The longer the bottle is kept in the refrigerator, the less ability it has to fight off growth of harmful bacteria inside.

For the best chances of lasting as much as possible, make sure to store the bottle towards the very back of the refrigerator.

Breast milk stored towards the back of the refrigerator as much as possible usually lasts longer than breast milk stored more towards the front of the refrigerator.

Previously Refrigerated

How long will breast milk that’s been previously refrigerated last outside will also greatly depend on how long it’s been in the fridge in the first place.

As a general rule of thumb for you to follow, the longer breast milk has been in the fridge, the less it will last when placed outside, and vice versa.

For this reason, try to only take out a bottle of breast milk from the fridge when you want your baby to feed from it right away.

Refrigerator Lifespan

How long you can keep your breast milk in the fridge will also greatly depend on whether or not you’ve previously left it to sit outside for a while before.

If you haven’t done that, then its lifespan in the fridge will be longer.

On the other hand, the longer you’ve left it to sit out before, the less time you’ll have before it goes bad even when you store it in the fridge.

Freezer Lifespan

If you don’t plan on putting a bottle of breast milk to use anytime soon, it’s best that you store it in the freezer instead of the refrigerator.

When you pump breast milk and properly store it in a freezer straight away, you can still take it out and have your baby feed from it anytime during the next 6 months.

It’s arguable that you could even have a 12 month window to take advantage of when storing breast milk in a deep freezer, but experts agree that limiting yourself to a 6 month window is a much safer option.

After the 6 months mark, the milk will begin to lose a significant portion of its nutritional profile and properties it has that fight off bacterial growth.

An important note to make here is that if you’re storing your breast milk in the freezer, try your best to store it as far back as possible.

The more you push it towards the back of the freezer and away from the door, the more time it will last, and the closer you have it towards the front side of the freezer, the less time it will last.

Ice Packs

If you’re having breast milk stored in an insulated cooler and are making use of ice packs, you have 24 hours to make use of before the milk goes bad and is not suitable to give your baby anymore.

How Can I Know If A Bottle Of Breast Milk Has Gone Bad?

Many experts argue that breastfeeding your baby in the most direct of forms is better for them, their health and their development than pumping breast milk into a bottle for later use whenever the need arises.

While this may very well be true, it doesn’t mean that you’re wrong for pumping breast milk into a bottle for later use.

Yes, fresh breast milk that’s fed to the baby directly from the mother’s nipple is the best way you could go, but it’s not the way every mother out there could go.

Some mothers have severe nipple sensitivity and cannot breastfeed directly without experiencing excruciating amounts of pain, other mothers have babies that cannot feed from their nipples efficiently no matter what, and so on.

Now, in an ideal world, you could remember the exact time it was when you pumped milk into that bottle, or heated one up.

However, we both know that this is far from a perfect world we live in and things aren’t that easy, so how can you make sure the bottle is still good to give your little baby?

Jot Down Timings

Keep a small piece of paper or notebook with you where you regularly keep track of whenever you pump breast milk into a bottle or heat one up.

Note from Michelle Roth, BA, LCCE, IBCLC: “A dry erase board on your refrigerator or an app on your smartphone might also be useful for this.”

This way, if you’re still not done pumping and something immediately comes up where you have to stop it halfway, or you’ve heated up a bottle of breast milk but had to attend to something else on the spot, this note of timing will give you a clear answer later about whether the bottle is still good to give your baby or not.

This is the best way to get an accurate answer, as relying on memory isn’t the best or most accurate method to follow.

Even better, start a habit of labeling the date on each and every bottle of pumped breast milk you fill as soon as you’re done with it.

Marking the date on a partially finished bottle becomes extra important so you don’t get mixed up when you re-attend to it, and end up adding freshly pumped breast milk to a bottle that’s on the verge of going bad.

Go By Your Sense Of Smell

In cases of doubt like this, and this is true when it comes to almost any kind of food or drink out there, go by your sense of smell.

If you take a couple of sniffs and detect a bad smell, then chances are your senses are right and you should dispose of the milk.

The good news for you is that the smell test is pretty easy when it comes to breast milk, as breast milk that’s gone bad leaves an awful smell that’s strong enough for anyone to notice right away.

Go By Your Sense Of Taste

Even though we wouldn’t recommend you do this right away before trying to go with the sense of smell test, you could detect breast milk that’s gone bad through the taste test as well.

The good news is that you won’t have to drink the whole bottle before determining whether it’s gone bad or not, a minimal taste sample will do just fine. If it’s gone bad, you should immediately notice a strong and sour taste.

Why Should I Not Keep My Breast Milk Outside For A Lot Of Time?

Now that we’ve answered the questions of how long will breast milk last outside the refrigerator before it goes bad and how you can tell exactly if it’s gone bad or is still good to give to your little one, let’s talk a bit about the reasons why you shouldn’t leave this milk sitting outside for too long.

Degraded Nutritional Profile

Whenever you pump breast milk, the more time passes and your baby still hasn’t been fed from that bottle, the more its nutritional profile will suffer and degrade.

Namely, it’s the Vitamin C in this milk that will suffer most, and that’s definitely not a good thing for little baby’s development.

This is true in all cases, regardless of whether you freshly pump breast milk into a bottle and store it in the fridge/refrigerator for future use, or you keep it outside for a while.

The more time passes by and your baby hasn’t fed from your pumped breast milk, the more vitamin C it will lose as a result.

Decreased Ability To Fight Off Harmful Bacteria

A general rule of thumb for you to know and follow is that the moment you finish pumping breast milk into a bottle, that’s when the milk in this specific bottle will have the strongest ability to fight off harmful bacteria from forming.

Wherever you store the bottle from there on, the same rule applies to all scenarios: The older the milk in the bottle gets and the more it ages, the less ability it will have to fight off these harmful bacteria from forming, and the more dangerous it will be for your baby to drink.

Where you store the milk is the main factor in determining how long it’ll be good for, but there’s no place you could ever store it in where these harmful bacteria don’t start forming after a certain amount of time.

Why Can I Feed My Baby Breast Milk Hours & Days After It’s Expressed?

In case you’re wondering about what properties breast milk contains that keeps it good enough to feed your baby hours, and sometimes even days, after it was expressed – it’s the antibodies and live cells it contains.

These antibodies and live cells work to prevent harmful substances (such as bacterial or fungus) from forming inside the milk, hence prolonging its lifespan.

This isn’t true when talking about formulas for babies, on the other hand, as formulas don’t have these antibodies and live cells to combat bad bacteria from forming.

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Medically Reviewed By: Michelle Roth, BA, LCCE, IBCLC

Medically Reviewed By: Michelle Roth, BA, LCCE, IBCLC

Michelle Roth, BA, LCCE, IBCLC is a board-certified lactation consultant for two busy pediatric practices. She is a former La Leche League Leader, Lamaze Certified Childbirth Educator, and Certified Infant Massage Instructor. She has taught classes ranging from healthy pregnancy, to childbirth preparation, to parenting, and more.

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