Pumping 101: How to Tell if Your Breast Milk’s Gone Bad

Are you a nursing mom? Do you pump your milk and store it for later use?

If so, do you think you’d be able to tell whether or not it’s gone bad?

Though there are some similarities, human milk isn’t identical to traditional dairy milk; its appearance, smell, and even taste can be vastly different. So, it might be more difficult than you realize to identify spoiled breast milk.

Table of Contents

    Storing Breast Milk Guidelines

    There are two phases of breast milk: “fresh” and “usable.”

    “Fresh milk” is exactly what it sounds like – recently pumped, at its peak of freshness, and full of the nutrients and antibodies typical of breast milk.

    “Usable milk” is past its ideal period (immediately after pumping) but still fine for your baby. It has been stored properly in the refrigerator or freezer, does not harbor bacteria, and will not threaten the health of your baby. You can guarantee nourishment to your little one, but some of the benefits may be diminished as it is no longer “fresh.”

    La Leche League league gives the following guidelines for milk storage (1):

    • Room temperature – 4 hours (ideal) to 6 hours (acceptable).
    • Refrigerator – 72 hours (ideal) to 8 days (acceptable).
    • Freezer – 3-6 months.
    • Deep Freeze – 6-12 months.

    The Rule Of Six

    When I first visited a lactation nurse, she advised me to remember “the rule of 6”.

    The rule of 6 means that breast milk can last:

    • 6 hours on the counter.
    • 6 days in the refrigerator.
    • 6 months in the freezer.

    While it’s possible my milk would last beyond those periods, under certain circumstances, “the rule of 6” was an easy way to remember safe storage timelines while caring for a newborn, and with too low mental energy to keep track of multiple guidelines and “freshness windows.”


    When following safe storage guidelines, remember changing the storage method does not re-start the storage clock. For example, if you’ve had milk in your refrigerator for eight days, tossing it in the freezer will not buy you another 6-12 months.

    If your milk had already been nearing spoilage in the refrigerator, freezing it will buy you additional time, but it will still spoil in the freezer faster than if you had frozen it immediately after pumping.

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    Factors Affecting Storage Time

    Two main factors impact the length of time you can effectively preserve milk.

    The first is temperature.

    Milk in the refrigerator should be stored near the back, where the temperature is coldest and most stable, not affected by the opening and closing of the doors.

    Take Note

    Breast milk should never be stored in the door of the refrigerator due to wilder fluctuations in temperature when doors are opened.

    Milk stored in a typical refrigerator freezer is said to last up to six months. If you have a standalone freezer (also known as a “deep freezer” or “chest freezer”), then milk can be kept for up to 12 months without spoiling because of the colder and more stable temperature (2).

    The second important factor is the storage container you choose. Store your milk in a commercially-made milk storage bag made specifically for freezing or in hard plastic bottles or glass bottles. Both should be clean and completely sealed before storing to prevent contamination, which can lead to milk spoilage.

    Understanding The Smell Of Breast Milk

    With regular dairy milk, the “sniff test” is often the most accurate measure of whether or not the milk has spoiled. However, with breast milk, it’s not so easy.

    The scent of breast milk is easily affected, so an unfamiliar smell doesn’t automatically mean it’s gone bad. It can also vary widely from woman to woman and even change from day to day in the same person (3).

    Things that affect the smell of breast milk are:

    • Food.
    • Medications.
    • Freezing process.
    • Storage containers.
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    The Taste of Breast Milk

    Because smell and taste are so closely linked, the same factors that affect your milk’s smell can also affect its taste. A mother’s diet is an especially significant factor – strong flavors, especially a “spicy” taste or pungent spices – can tinge a woman’s breast milk with that flavor.

    Understanding The Way Breast Milk Looks

    “Normal” breast milk comes in a rainbow of colors. Some of these colors are (4):

    • Yellow
    • Off-white
    • Blue-tinged
    • Slightly orange

    Breast milk color can even vary within the same pumping session. Much of the variance is due to the specific ratio of foremilk (thinner and more watery) to hindmilk (thicker and more fatty), which tends to change from morning to night.

    Still, other things like diet, medication, herbs, and hydration play a role, too. The important thing is that there is a wide range of “normal,” and a shift in color of your breast milk does not automatically make it bad.

    What if your milk looks pink? It’s possible that small cracks in your nipple that may be bleeding can make your milk look very red or pink, but this milk is still safe for your baby to drink. Working with a lactation consultant can help you determine the cause for the pink milk, as well as how to avoid it happening again.
    Headshot of Michelle Roth, BA, IBCLC

    Editor's Note:

    Michelle Roth, BA, IBCLC

    Identifying Breast Milk Gone Bad

    1. Look Closely

    Breast milk naturally separates after pumping, with the fat rising to the top and the water falling to the bottom. When milk is still good, it easily mixes with a gentle swirl of the bottle.

    If your breast milk remains separated or chunks float in it after attempting to re-mix, it has likely gone bad and it’s a good idea to toss it.

    2. Smell Your Breast Milk

    If you’ve stored it in the refrigerator or at room temperature, the “sniff test” could be a reliable way to determine whether your milk has gone bad.


    While variances in the smell are normal with breast milk, if yours smells rancid or like sour milk, it has probably gone bad.

    This method may not be reliable, though, if you’ve frozen your breast milk. Breast milk contains lipase which breaks down fats for your baby. In mamas with high lipase breast milk, the enzyme can cause thawed breast milk to smell sour or soapy, even though it is still perfectly safe (5).

    To test whether your milk tends to take on this scent, freeze a small amount of breastmilk for five days, then thaw it, and then test the scent. In the short timeframe which you’ll do this experiment, you can be confident your milk has not soured, and it simply tends to take on this smell after freezing, but is still safe for your baby.

    However, it’s worth noting that some babies will reject this milk. So, before freezing large batches of milk, it may be a good idea to feed some thawed milk to your baby to see whether or not they will accept it. If they won’t, you can eliminate this issue by scalding your milk before freezing.

    To scald your breast milk:

    • Heat your milk in a small pan.
    • Wait until small bubbles form around the outside (approx. 180 degrees F).
    • Remove from heat.
    • Allow cooling.
    • Pour into containers and freeze.
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    3. Taste Your Breast Milk

    Similar to the previous “sniff test,” taste your breast milk. It will taste different than cow’s milk, but any flavor other than rancid/sour is acceptable.

    If you store your milk in the refrigerator and it tastes rancid or sour, it has likely gone bad and should not be fed to your baby.

    In the case of frozen milk, see the above steps to determine whether your milk tends to take on a sour (but safe) flavor upon freezing due to a high lipase. If this isn’t the case, but your milk tastes sour in one particular instance, throw away the milk as it has likely gone bad.

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    Has Your Milk Gone Bad?

    You work so hard to pump your milk, you don’t want a drop to go to waste. Following proper storage recommendations and understanding the variances in the appearance, smell, and taste of “normal” breast milk can prevent you from unnecessarily throwing out otherwise good milk.

    You need to be sure that the milk you’re feeding your babe won’t make them sick, and knowing how to test it for spoilage will do just that.

    Do you have any breastmilk gone bad stories or extra tips for testing spoiled milk? We’d love to hear in the comments below.

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    41 Reader Comments

    1. Brianna

      Hi. My milk has only been in the fridge for 2 days. I pumped and stored in the fridge right away. It hasn’t been frozen. But I noticed it smelled a bit “cheesy,” like sour milk, which I haven’t smelled from my milk before. It’s not that strong, just slightly smells that way. I tasted a bit and it tastes sweet, but the after taste is a tiny bit sour. Is it still good? It smelled like that only after a day of being in the fridge. I would rather not throw it out if I don’t have to, as I have a low supply.

      • Team Mom Loves Best

        Hi Brianna, we’d recommend being safe than sorry. Usually, breast milk stored in the fridge should be good for six days. But, since we can’t taste or smell yours, we’ll have to leave it to you. If your mama instinct says it smells/tastes funny, it’s probably better to chuck it. For next time, though, try storing it at the back area of your fridge. Sorry to hear about your low supply! Have you seen our post about increasing supply? Please let us know what you decide to do!

        • mama S

          Fenugreek & Blessed Thistle Herbs should help increase your supply. If not, Domperidone may help. It’s a prescription you can ask your health care provider or health nurse for.

    2. Joanne Sosa

      Hello! I have a question regarding how can I identify that the breast milk went bad after being frozen. Hi. My milk has only been frozen for almost 4 weeks after I pumped and stored in the fridge (frizer) right away. I took it out yesterday and left it to that in the fridge and when I was going to use it in the morning it looked yellow-ish, granular (like corn flour), and the smell was not promising. Have you heard something like this before? I’m a new mom and all this is totally new to me.

      • Team Mom Loves Best

        Hi Joanne! Thanks for reading! The truth is that breast milk naturally separates after pumping, with the fat rising to the top and the water falling to the bottom. The same is expected when frozen. However, when milk is still good, it easily mixes with a gentle swirl of the bottle. So, if your breast milk remains separated or chunks float in it after attempting to re-mix, it has likely gone bad and it’s a good idea to toss it. You also mentioned the smell? While variances in the smell are normal with breast milk, if yours smells rancid or like sour milk, it has probably gone bad. We hope this helped you! Please keep us posted 🙂 And congrats on being a new mom 🙂

    3. Abbey


      So, my thawed milk smells strongly of plastic (possibly from the storage bags) now I know about lipase but it doesn’t smell soapy. If it IS from the plastic bags, is it no longer safe for baby?

      • Team Mom Loves Best

        Hi Abbey! It’s hard to say, but overall, plastic doesn’t have the best rap nowadays. Perhaps switch storage bag brands? Let us know how it goes, and thanks for reading 🙂

    4. Susie

      The milk I just accidentally gave my daughter was warmed and fed to her yesterday. The bottle wasn’t put in the fridge until 9 pm last night and was left out. This morning, the housekeeper put that milk in the fridge. I warmed it this morning and gave it to my daughter. I realized this about an ounce and a half later. I took it away and she cried for more. If she wasn’t rejecting it, will she be ok? Does this mean it may not be bad? It didn’t smell bad.

      • Team Mom Loves Best

        Hey Susie, thanks for reading. If it didn’t taste bad to you, it probably wasn’t. We hope it all worked out well!

    5. Shravani


      I have stored 60 bags for my babe. They are mostly from Nov and Dec of 2018. I tried to thaw them. I could see the yellow layer separate from the milk and after mixing it up well, it still forms the yellow layer at the top. Does it mean my milk gone bad ??

      • Team Mom Loves Best

        Hey Shravani, yes, it appears your milk may have gone bad. When milk is still good, it should mix easily with a gentle swirl of the bottle. If your breast milk remains separated or chunks float in it after attempting to re-mix, it has likely gone bad and it’s a good idea to toss it.

        • Shravani

          Can you please explain how exactly I should use frozen milk to feed the baby?

          • Team Mom Loves Best

            Hi Shravani, I’m not sure I understand your question. Which part of the process do you have issues with exactly?

    6. Linda

      The milk I’ve thawed often smells metallic, so I tasted it to be sure it was okay. When I taste it, it frequently leaves a weird taste in my mouth, almost vegetal. Is this normal, or does it mean my milk has gone bad after just 2 months in the freezer?

      • Team Mom Loves Best

        Hey Linda, thanks so much for reading. We really can’t be sure. Most moms would be in the best position to tell. The general rule, though, is to toss when in doubt. So, if you are, we’d advise tossing. We hope that helps 🙂

    7. Wilson

      Hi, I stored my milk in the back of the fridge like I was told, but when I opened it it had this weird sizzling sound. Any idea why this is?

      • Team Mom Loves Best

        Hi LaToya, we can’t say for sure, but tasting and smelling the milk may help you figure out if it’s still good. If in real doubt, it’s probably just best to toss it — sadly 🙁

    8. T Vijithra

      Hi, can I store my breast milk in a silver container?

      • Team Mom Loves Best

        Hey T, thanks for reading. It’s generally best to store milk in the fridge in specially designed glass bottles or BPA-free plastic bags. You can find a few safe options in our post about breast milk storage bags. We hope this helps 🙂

    9. Hello! A strap got caught in our deep freezer door which caused it not to seal. Everything in the freezer thawed before we realized it, to include a lot of breast milk (to say I was devastated is an understatement). It was all still cold so I put it in our small freezer in desperation to refreeze it. Do you think it’ll be ok?

      • Team Mom Loves Best

        Hey Jerra, we can imagine. It might still be okay, but it depends on how long it was unsealed for. As the article says, the shelf life depends on how long and the conditions under which it’s stored. So be sure to use this batch up quickly, just to be on the safe side 🙂

      • Katelyn Young


        I pumped milk yesterday throughout the day and froze what was left overnight. This morning I put it in a cooler between icepacks from noon to 7. When I opened the cooler the packs were just ever so slightly thawed. Like slightly more frozen than a blended margarita. I poured what had thawed from one of the bags and heated it. I served it to her cooler than room temp. But even at that point, a swish of the bottle didn’t make what looks like granulars of fat disappear. Could this be because I poured it from a pack that was still half frozen? I know it was colder than a fridge in a cooler since even after 7 hours it was more frozen than not and all pumped yesterday.

        Thank you

        • Team Mom Loves Best

          Hi Katie, thanks a lot for reading. It’s tricky to say, because generally when milk is still good, it easily mixes with a gentle swirl of the bottle.
          So if your breast milk remains separated or chunks float in it after attempting to re-mix, it has likely gone bad and it’s a good idea to toss it. But in your case, if you believe it’s still good, smelling it might confirm your beliefs. It might just be your reheating and cooling process at fault. We hope it all worked out well in the end. We’d love to know what you decided to do, though — if you’d like to share 🙂

    10. Maribel

      Is it normal for freezer-stored breast milk to look greasy after thawing and warmed up?

      • Team Mom Loves Best

        Hey Maribel, “greasy” isn’t a word we’d use. It may separate into layers and need to be shaken to mix properly, but if in doubt, it’s always better to be safe rather than sorry! We hope that helps 🙂

    11. Is it ok to pump and store the entire day’s milk in the same container in the fridge?

      • Team Mom Loves Best

        Hey Kim, we’re not sure exactly what you mean. Could you please explain? Remember, though that milk will only stay 8 days, max in the fridge. Each batch you pump will have the same shelf life, i.e. “older” milk will go bad before “newer” milk. Hope this helps.

    12. Hi there. When I defrost my milk, the smell makes me so sick I can’t stand it. My baby doesn’t seem to mind and it doesn’t make him sick and I also ensure it mixes well without any leftover separation. I don’t believe it’s off but I can’t stand to feed him as I feel like vomiting just from smelling it. Any tips?

      • Team Mom Loves Best

        Hey Bec, we’re sorry to hear about your difficulty with the smell of breast milk. You’re certainly not alone as some women and even their husbands dislike the smell as well. If you’re really put off by it, it may help to put a bit of essential oil under your nose while you defrost the milk — just to mask the smell.

        Thankfully, you won’t have to face breast milk all your life. So hang in there, mama! 🙂 We’re rooting for you.

    13. mama S

      I pumped some milk last night. I believe I left it out overnight for a few hours after the 6 hr mark. Then when I smelt it, it kind of smelt like dirty feet. I didn’t think anything of it and just stored in freezer. I’ve been thinking about this decision all day whether or not I should toss this milk. I had 3 bottles in the freezer, thawed one earlier today and it seemed to have smelt fine, but my daughter just choke/puked it up about an hr.5 ago. I’m debating giving it back too her. I will probably just thaw smell and dump all them just to ensure she doesn’t become ill.

      • Team Mom Loves Best

        Hey Mama S, yes, we’d certainly recommend tossing the milk if you can tell that it smells funny. Better safe than sorry! All the best 🙂

    14. Tina

      Hi there,

      I’m a new mom here.
      I have some milk stored away in the freezer. There have been a few bags about 2 months old and they taste sour. Sometimes my baby takes it some times he doesn’t.
      Recently I pulled out a bag that is a week old just to test if I have high lipase. And it was fine. Not sour taste no sour smell.
      I really need help here on this because I don’t want to throw out all of the bags that are a couple months old. Unless ofcourse I need to.

      • Team Mom Loves Best

        Hey Tina, we can imagine that you don’t want to lose all your precious milk and that’s really a tough spot to be in. No one can tell you whether or not your milk is sour — only you will know that. So if your gut says there’s a chance the milk has gone bad, we’d definitely say better safe than sorry! We wish you all the best though and would love to know how everything works out.

    15. Tina

      Hi there, I’m a new mom here and I need some help on my milk.

      I’ve been pumping and freezing my milk for a couple months now.

      I’ve recently noticed that a couple bags of milk I pulled out from a couple months ago tasted sour.

      I wanted to test if my milk had high lipase. So I pulled out a bag that’s a week old and it tasted fine. No sour taste or smell.

      The freezer I’m currently using is a pull out that is attached to the fridge. The temperature is set to -17.

      I really don’t want to throw out those milk bags that are a couple months old unless I need to.

      • Team Mom Loves Best

        Hey Tina, we can imagine your stress. It’s really hard for anyone besides the mom to know when the milk has gone sour. If it tastes/smells good to you, then it probably is. We wish we could be of more help, but generally, it’s better to be safe than sorry!

    16. Maria Aurianne Adeline Saranillo


      May I just ask what is the meaning of frozen breast milk with white spots? The milk is frozen for two months now.

      • Team Mom Loves Best

        Hi Maria!

        Thanks for reading 🙂 The thing about breast milk is that it naturally separates after pumping — the fat rises to the top while the water rests at the bottom.

        When the milk is still good, it should easily mix again when you swirl the bottle. But if your breast milk remains separated or chunks/white spots float in it even after you’ve tried to re-mix, it’s probably gone bad. It also makes sense to smell the milk just to double check. If your gut strongly tells you that the milk is still good, it’s really your choice to make.

        We hope this helps, Maria. Please let us know how it goes, and all the best!

    17. Charlie M

      I have 3 months’ worth of breast milk in the freezer that I think may have gone bad. I have not kept up with the pumping schedule since I have been home with my LO, but I’m going back to work and worried my supply won’t be sufficient enough to pump at work. What are some natural things I can do to increase supply?

      • Team Mom Loves Best

        Hi Charlie, that’s quite a challenging situation. Going back to work can be tough on moms for a variety of reasons — this one included! But we’re happy to help. We recommend eating some of these foods to increase your supply. You’ll also find 25 tips for increasing supply here. Feel free to check out the main “Increasing Milk Supply” section for more help. If you’re looking for a specific recommendation, fenugreek is highly rated among our moms as a lactation booster. We hope you find these helpful! Please let us know if you need more information 🙂 All the best.

    18. Jen

      Hi there, I have started to thaw the frozen milk I have for my little one and she drank it without a problem. When I was burping her I noticed her breath smelled like metal. I smelt and tasted the breast milk and it tasted very bad (very metallic-like). I’ve read it’s safe for them to drink and it has not gone bad but I feel bad giving it to her because it tastes so metallic. Advice? Tips? 🙏

      • Team Mom Loves Best

        Hi Jen, well done on finding out more about the metallic taste in the milk. You’re right that that sour/metallic taste can be caused by lipase (which is normal) in breast milk. It may seem off to you, but it’s perfectly fine for your baby. However, if this is still an issue for you, you can eliminate this issue by scalding your milk before freezing. You’ll find a YouTube tutorial for that embedded in this post. But don’t stress about it at all, mama, you’re doing a great job!

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