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.

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 (source):

  • 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 (source).

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 (source).

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 (source):

  • 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 (source).

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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10 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!

  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. 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?

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