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. Because of this, it might be more difficult to identify spoiled breast milk than you realize.

Here’s what you need to know to prevent feeding your baby breast milk gone bad.

How Long Can I Store Breast Milk?

When talking about breast milk, it’s important to understand that there are two different phases: “fresh” and “usable.”

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

“Usable milk” is past its ideal period (immediately after pumping) but is still fine for your baby. It has been stored properly in the refrigerator or freezer. It does not harbor bacteria and will not threaten the health of your baby. It will still provide nourishment to your little one, but some of the benefits may have 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

When I first visited a lactation nurse, she tried to make it easier on me by advising me to simply 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 entirely probably that my milk would last beyond those time periods in certain circumstances, “the rule of 6” was an easy way to remember safe storage timelines in the midst of caring for a newborn and not having the mental energy to keep track of multiple guidelines and “freshness windows.”


One thing to keep in mind when following safe storage guidelines is that 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.

Because your milk had already been nearing the point of spoilage in the refrigerator, freezing it will preserve it for some additional time, but it will still spoil in the freezer faster than if you had frozen it immediately after pumping.

Related Reading: 33 Proven Ways You Can Pump More Milk

What Factors Impact the Length I Can Store Breast Milk?

There are two main factors that impact the length of time you can effectively preserve milk.

The first is temperature.

Just as milk in the freezer lasts longer than milk in the refrigerator because it is colder, nuances within both the refrigerator and freezer will affect storage times specific to those appliances.

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.

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

Milk stored in a typical refrigerator freezer is said to last up to 6 months. If you have a standalone freezer (also known as a “deep freeze”) then milk can be held for up to 12 months without spoiling due to the colder and more stable temperature (source).

The second factor that impacts the length of time you can store breast milk is the storage container you choose.

Ideally, you will store your milk in a commercially-made milk storage bag or hard plastic bottle. These items should be clean and completely sealed before storing to eliminate the risk of contamination, which can lead to milk spoilage.

What Factors Impact The Smell of Breast Milk?

With regular dairy milk, the “sniff test” is often the infallible measure of whether or not the milk has spoiled – anything that doesn’t smell “normal” means something is wrong.

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. The smell of breast milk can vary widely from woman to woman – and can even change from day to day in the same person.

Things that affect the smell of breast milk are (source):

  • Food
  • Medications
  • Freezing process
  • Storage containers

More in Breastfeeding: What are the Best Lactation Supplements?

What Factors Impact 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.

What Factors Impact the Appearance of Breast Milk?

“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) and hindmilk (thicker and more fatty), which tends to change from morning to night.

Still other things like diet, medication, herbs, and hydration can all play a role, too. The important thing to remember is that there is a wide range of “normal,” and simply noticing a shift in color of your breast milk does not automatically indicate that it’s gone bad.

How To Tell If Breast Milk Is Bad

1. Examine the Appearance of Your Breast Milk

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 back together with a gentle swirl of the bottle.

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

2. Smell Your Breast Milk

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


Variances in smell are normal in breast milk – but if yours smells rancid or like sour milk, it has likely gone bad.

This method may not be the most reliable, though, if your breast milk has been frozen. Because of chemical changes that happen when the enzyme lipase is frozen and begins to break down the fat in the milk, thawed breast milk can omit a sour smell – even though it is still perfectly safe – if your milk contains high levels of this enzyme (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. Because of the short timeframe in which you’ll do this experiment, you can be confident your milk has not soured in that short amount of time and that your milk simply tends to take on this smell after freezing, but it is still safe to give to your baby.

It’s worth noting that some babies will reject this milk. Prior to freezing large batches of milk it may be a good idea to give 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 prior to freezing.

To scald your breast milk, do this:

  • Heat your milk in a small pan
  • Wait until small bubbles form around the outside (approx. 180 degrees F)
  • Remove from heat
  • Allow to cool
  • Pour into containers and freeze
Related Reading:
How to Heat Breast Milk Safely

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 your milk tastes rancid or sour, it has likely gone bad and should not be fed to your baby.

If you freeze your milk and it tastes sour when thawed, 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 you find that your breast milk does not usually have the propensity to taste sour, but it tastes sour upon checking in one particular instance, throw away the milk as it has likely gone bad.

Related Reading:
Cold Remedies You Can Take While Breastfeeding

Has Your Milk Gone Bad?

If you’re wondering whether your breast milk has gone bad, you should:

  1. Examine it.
  2. Smell it.
  3. Taste it.

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

But still, at the end of the day, 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.

Share this with a breastfeeding mama in your life!

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? It's not always as easy as you might think. Click here to learn what you need to know to prevent feeding your baby breast milk gone bad. #breastfeeding #breastmilk #baby #motherhood #momlife #parentingtips

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