Breast Milk Storage: How Long Can Breast Milk Sit Out?

How long can breast milk sit out? And how long will it last in the fridge? Get answers to these questions and more in this post on safe breastmilk storage.

How Long Can Breast Milk Sit Out Photos and Info by Mama Natural

If you’re pumping breast milk for your baby, you may be wondering, how long can breast milk sit out? And how do I store it?

First of all, good for you! Breastfeeding isn’t always easy, but you’re making sure baby is getting the very best food even while you’re away. In this post, we’ll unpack how long breast milk can sit out, plus answer some breast milk storage questions.

How long can breast milk sit out?

It’s always best to refrigerate or freeze milk right away, but what if you’re at work? Or what if you forgot about a bottle on the counter? Luckily, breast milk is a live food that can withstand being left out for a relatively long amount of time.

Fresh milk

Freshly expressed milk can be stored at room temperature for 6–8 hours. If the room is particularly warm, it’s more like 4 hours.

Insulated cooler

Freshly expressed milk can be stored in an insulated cooler with an ice pack for 24 hours.


Fresh milk can be stored in the back of the refrigerator for 3–8 days (assuming it was collected as carefully as possible). Ideally, it should be used or frozen within 3 days. Thawed milk can stay in the refrigerator for 24 hours. Don’t refreeze.


Fresh breast milk should be stored in the back, away from the door, and should be used within 6 months.

Deep freezer

Fresh milk can be stored in a deep freezer for 6–12 months.

Tips for pumping and storing breast milk

If you are pumping breast milk for baby, there are a few guidelines that will make life much easier and ensure that your milk is safe.

  • Wash hands before pumping.
  • Use containers that were properly sanitized with warm water and soap.
  • Store milk in 1–2 oz amounts (or whatever you know your child will finish at a feeding).
  • Leave an inch or so of space at the top for expansion if putting in the freezer.
  • Date each container.
  • Freeze or refrigerate as soon as possible. If a refrigerator isn’t available, an insulated cooler is the next best choice.

Get free updates on baby’s first year! – Free Updates on First Year [In-article]

Sign me up!

Thawing and heating frozen milk

The best way to thaw frozen breast milk is gradually in the refrigerator. If that’s not an option, then place the bottle of frozen milk in lukewarm water (or hold it under the tap). Increase the temperature of the water slowly until the milk is no longer cold (but not hot). Here’s more information on how to warm breast milk.

Never microwave human breast milk. The microwave may cause hot spots in the milk that can be very dangerous for baby’s sensitive mouth. Microwaving may also destroy some of the antibodies in the milk. Who wants that?!

Keep in mind that once milk is refrigerated or frozen, it loses some of its antioxidants and bacteria-fighting abilities. It’s still the very best food for baby but will not last as long as fresh milk.

Can leftover breast milk be served?

The potential problem with serving leftover milk is that bacteria from baby’s mouth may enter the bottle and contaminate the milk, so it’s best to avoid feeding leftovers if possible.

However, many moms have trouble with this answer, since breast milk is like liquid gold, and wasting even a small amount is devastating to a pumping mom. Many sources say that despite the possibility of bacteria growth, it is safe to feed leftover breast milk.

One study found that some breast milk that was refrigerated for 8 days had less bacteria than when it was expressed. This is because breast milk contains live cells and antibodies that help fight bad bacteria.

According to Ruth Lawrence, MD, author of Breastfeeding, A Guide for the Medical Professional:

“Breast milk can safely stand at room temperature for 6 to 8 hours and need not be discarded if the first feeding attempt is incomplete. In contrast, formula must be refrigerated and discarded after the first feeding attempt because it contains no antibodies or infection protection factors.”

So, a good rule of thumb is to avoid feeding leftovers by storing breast milk in smaller amounts. If you do feed leftover breast milk, offer it within a few hours of the last feed, ideally (possibly up to 6–8 hours later).

How Long Can Breast Milk Sit Out? (Breast Milk Storage)

Final thoughts on breast milk storage

Human milk is pretty amazing. It can sit out for much longer than any other food and still be safe. It can be frozen and still be nutritious. What kind of a wonder food is this?! Oh, right—nature’s perfect food for baby, which comes from your amazing bod, mama!

So, next time you leave some breast milk out accidentally, you likely won’t need to throw it away. Considering how much time and energy it takes to pump that precious liquid gold, that’s music to the ears!

Genevieve Howland

About the Author

Genevieve Howland is a childbirth educator and breastfeeding advocate. She is the bestselling author of The Mama Natural Week-by-Week Guide to Pregnancy and Childbirth and creator of the Mama Natural Birth Course. A mother of three, graduate of the University of Colorado, and YouTuber with over 130,000,000 views, she helps mothers and moms-to-be lead healthier and more natural lives.


  1. Can I add another layer (maybe an ounce or two) of freshly expressed milk (but cooled first in the fridge) to an already frozen jar?

  2. If I take a bottle out the fridge of breast milk warm it, but she only eats a few oz and falls asleep! How long is that bottle good for being left out at room temp, Incase she wakes up in the next hour or so is it still good to feed left out hours later!

  3. New mom and a bit confused about this ‘fresh milk can be refrigerated’. So does it have to be refrigerated right after being pumped, or can it sit for say 5hrs, use it to feed baby, baby didn’t finish, throw it in a bag and into the fridge so it doesn’t go to waste?

  4. Aloha! Hubby took 40 oz of frozen breast milk out of the freezer and forgot it until this morning, 8 hours later. It was on a tile floor in our downstairs which generally feels cool since it’s surrounded by cement. Milk was stacked and still felt cool this morning when he found it. We live in Hawaii and it’s been cold for us at night which is in the 60s. He mixed it and it mixes evenly and also smelt and tasted it and said it tasted normal. Is this milk safe for our little one to drink? Thanks so much for the help!!

  5. I left refrigerated breast milk in the diaper bag for almost 8 hours. It doesn’t smell spoiled or bad. Is this too long to leave out at room temperature? It was 70 degrees in the house the whole time. The diaper bag does say it’s insulated.

  6. Breast milk that has been put in the fridge. If I take it out how long can I leave it out for before I can use it?

  7. Honestly, this is amazing, just trying to get the right information this whole thing but at last I’ve got the answer…tanx 4 ur lectures

  8. Can I keep milk in freezer after 5 hours of expressing?

    • Yes!

  9. How long can warm milk stay out?

  10. I pumped around 7:30, fell asleep, and woke up at 3! Can i still put the milk in the fridge? I read 6-8 hours but I’m nervous?

  11. If my baby leaves ~1 oz of breastmilk in the bottle from a feeding, am I better off putting that milk back in the fridge or leaving it out to use with his next feeding 3 hours later?

    Thanks for any insights!

    • **When milk for the first feeding came from the fridge (not fresh)

  12. Hi after I thaw my milk in the fridge I take it out and warm it up in the bag in the bottle warmer , is that ok ? how long can I keep it out t _ ? And feed him ? My baby eats 2 -3 ounces then whatever is left so he takes a while ?

    • I would only warm what your baby will eat per feeding. I don’t advise warming in a bottle warmer while still in the bag.

  13. I need some help is the breast milk still fresh even though I just pump twice a day my breast not producing much milk just only 1 oz what do I gonna do that I can have lot of milk.Your response is appreciated

    • You can combine cold breastmilk from two sessions, then freeze to store.

    • Hey! I just wanted to also let you know (although you may have found out by now since it’s a few months later) it’s totally normal for your breasts to only produce about 1-2 ounces (from both breasts combined) in the first month or two…then as your baby starts to need more to drink they will start to produce more in response to how much he drinks. Also, baby is much better at getting milk out than a pump is, so it may look like you’re not producing a lot but he/she is actually getting more than you think. I was so worried about low milk supply for the first month and a half because I would get at the most 1oz from one breast and half an ounce from the other, after 30 minutes of pumping. But as my baby grew (and I do breastfeed straight from the breast as often as I can, which is most of the time) when I would pump I gradually found that if my breasts were full I would get 2-3 ounces between the two of them, and now it’s up to almost 4 ounces (in 20 minutes of pumping) and my baby is 3.5 months old. Hope this helps!

  14. My wife took breast milk out of the freezer she pumped (80oz) placed in fridge for 5 days by mistake. (We left for vacation) Is the milk bad now?

    • It should be, you can smell and/or taste it to be sure.

  15. Once i thaw out a bag of 6oz breast milk and heat it up and give my baby 20z of the 6, do I need to put the remainder back in the refrigerator? how long is that good for? can it be reheated for next feeding? can i leave it out for next feeding?

  16. I have a question on freshly pump breastmilk. Understand it can leave 6-8hrs at room temperature. Is this mean within this 6-8hrs I can safely feed the baby in multiple times (in separate feeding bottle) without reheat them? Or each time feed I need to reheat it first (even still within 6-8hrs period)?

    Looking forward to your advise.

    • I personally would warm up what I would be feeding my baby, then pop the remainder in the fridge.

      • How about if I keep the small amount milk in bottle and in warmer till my baby cry for feeding? How long can we have the bottle in warmer? 1-2hrs in warmer is fine?

        Looking forward to your reply. Thanks

  17. if i leave out my breast milk for 3 hours can i still put it in the freezer ?!

    • Absolutely!

  18. Great reading. Found answers to my query our found it very reassuring that I’m doing a right thing. Thank you

  19. I have a question, I had 20 oz of frozen breast milk put in on a cooler bag , ended up not using it . Stayed in the bag for 12hours. It was thawed by the time I got home. I put it back in the freezer. Is it okay to feed my baby with this milk?

    • If it was still cold when you took it out of the bag it could be fine. I would for sure smell and taste it before giving it to my baby. If it smells even a little off, I would just give baby a nice milk bath with it instead.

  20. Wow very informative I thought I wasn’t going to find the answer I was looking for but instead I was amazed. Thank you reading the thawed breast milk tips and what to do after you heat it and now i know i was worried but your website gave me reassurance.

  21. Liquid Gold indeed, I’m no longer pumping for my 11 month old, we are down to just nights and mornings nursing sessions , however I always had trouble transporting frozen milk to my babysitter. The milk would always slightly thaw between my house and theirs and if it was refrozen it would go bad. I never could figure out what I was doing wrong.

  22. Thanks for the handy list. I always thought 4 hours for room temp, but nice to know it will be ok for a little longer if I ever really need it 🙂

    • Thanks for the handyl list it is very helpful for me

Add Comment

Your email address will not be published. All fields are required *


Hey Mama! Get my FREE baby updates every week!

  • Track baby’s development
  • Discover safe & natural remedies
  • Access free tools & resources


Not on Messenger? .