How to Tell If Your Breast Milk Has Gone Bad (3 Easy Tests) (2023)

Stored breast milk is like liquid gold. You want every ounce to benefit your baby. But if you don’t know how to tell if breast milk is bad, you may end up tossing perfectly good milk, or worse, feeding your baby compromised milk.

Though there are some similarities, human milk isn’t identical to cow’s milk. Its appearance, smell, and even taste can be vastly different.

We’ve consulted the experts to bring you the following facts about breast milk storage. We’ll outline three factors you can use to identify expired breast milk so you don’t have to worry about wasting good milk or making your baby sick.

Key Takeaways

  • Breast milk can be stored in the refrigerator for 72 hours (ideal) to 8 days (acceptable) and in the freezer for 3-6 months, and deep freeze for 6-12 months.
  • The rule of 6 is a simple way to remember safe storage timelines for breast milk.
  • Temperature and storage containers are the two main factors that affect the length of time breast milk can be preserved.
  • Breast milk should be stored near the back of the refrigerator and should be stored in commercially-made milk storage bags or clean, sealed, hard plastic bottles or glass baby bottles.
  • The smell of breast milk can vary widely, and an unfamiliar smell doesn’t always mean it’s gone bad.

Table of Contents

  • Guidelines for Storing Breast Milk
  • Factors Affecting Storage Time
  • Understanding The Smell Of Breast Milk
  • The Taste of Breast Milk
  • Understanding The Way Breast Milk Looks
  • Identifying Breast Milk Gone Bad
  • FAQs
  • Has Your Milk Gone Bad?

Guidelines for Storing Breast Milk

How to Tell If Your Breast Milk Has Gone Bad (3 Easy Tests) (1)
There are two phases of breast milk: “fresh” and “usable.”

Fresh milk is exactly what it sounds like — recently pumped milk at its peak of freshness, 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 that under certain circumstances my milk would last beyond those periods, the rule of 6 was an easy way to remember safe storage timelines. It helps to track guidelines and “freshness windows” when you’re caring for a newborn and mental energy might be low.


When following safe storage guidelines, remember 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.

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: temperature and storage containers.

Milk should be stored near the back of the refrigerator, where the temperature is coldest and most stable and less 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 the wilder fluctuations in temperature when doors are opened.

Milk stored in a 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”), milk can be kept for up to 12 months without spoiling because of the colder and more stable temperature.

Store your milk in commercially-made milk storage bagsmade specifically for freezing or in hard plastic bottles or glass baby 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 (2).

Things that affect the smell of breast milk are:

  • Foods the mother has eaten.
  • Medications the mother was taking.
  • Freezing process.
  • Storage containers.

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 flavor a woman’s breast milk.

Understanding The Way Breast Milk Looks

Breast milk comes in an array of colors (3). Some of these colors are:

  • 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 to hindmilk which tends to change from morning to night. Foremilk is much thinner and more watery, whereas hindmilk is thicker and fattier.

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

What if your breast 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.

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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 watery portion falling to the bottom. When milk is still good, it easily mixes with a gentle swirl of the baby 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 if your breast 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 (4).

To test whether your milk tends to take on this scent, freeze a small amount of breastmilk for five days, then thaw it and smell it. Because of the short timeframe, you can be confident your milk has not soured. If it smells sour, you can know your breast milk 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 to cool.
  • 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 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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What Happens If a Baby Drinks Spoiled Breast Milk?

Spoiled breast milk causes stomach upset, vomiting, and diarrhea in babies. The high fat content in breast milk makes it more susceptible to spoiling, especially if it’s not stored properly.

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What Color is Bad Breast Milk?

While the color of breast milk can vary depending on your diet and other things, spoiled breast milk often has a sour or rancid smell and can look yellowish or bluish in color. Fresh breast milk typically has a creamy white or slightly yellowish color.

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What Can I Do with Spoiled Breast Milk?

If you suspect your breast milk has gone bad, it’s best to just dispose of it. This might seem like a waste or disappointing for mothers who have issues with pumping, but it’s important to give your baby fresh milk.

You can pour it down the drain or use it to water plants. Do not feed it to your baby or donate it to a milk bank.

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Why is My Breast Milk Watery?

Breast milk varies in consistency depending on how much fat is in it. Foremilk, which is the milk that comes first during a feeding, is thinner and waterier.

Hindmilk, the milk that comes later in the feeding, is thicker and creamier with a higher fat content. If your breast milk is consistently watery, you might have to increase your breastfeeding or pumping frequency to ensure that your baby is getting enough hindmilk.

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Can You Mix Different Days of Breast Milk?

It’s pretty safe to mix different days of breast milk but be sure to label the milk with the earliest pumping date and time so you know it’s used within the recommended time frame.

You can also refrigerate the milk from each pumping session separately and then combine it when you’re ready to use it.

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Can You Rewarm Breast Milk Twice?

Try not to rewarm breast milk more than once. This is because reheating can destroy some of the beneficial components in the milk and can increase the risk of bacterial growth. It’s best to only warm the amount of milk you think your baby will consume in one feeding to reduce waste.

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 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.

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How to Tell If Your Breast Milk Has Gone Bad (3 Easy Tests)? ›

Assuming that you've made sure your pump equipment is clean, after pumping or expressing some milk, smell it and taste it. Does it smell or taste sour, or does it smell fine and taste a bit sweet? If it does smell or taste sour, then it indicates the presence of rancid fats and chemical oxidation.

How can you tell if breast milk has spoiled? ›

Assuming that you've made sure your pump equipment is clean, after pumping or expressing some milk, smell it and taste it. Does it smell or taste sour, or does it smell fine and taste a bit sweet? If it does smell or taste sour, then it indicates the presence of rancid fats and chemical oxidation.

Can you test breast milk at home? ›

Milk Strips are designed to test the acidity in your breast milk in order to determine the levels of bacterial activity. You dip a test strip in a tube containing your breast milk, and then it tells you whether the milk is safe to feed, or whether it's expired.

Is there any test to check breast milk? ›

Culture and Sensitivity Aerobic test is performed on a sample of breast milk to evaluate the level of Culture of the pathogenic organisms in the breast milk. The test is performed to make sure for any Breast Infection once during the treatment and post treatment of Breast Infection.

What does high lipase breast milk look like? ›

Some possible changes include: Milk that has a soapy smell or taste. Milk that has a metallic smell or taste. Milk that has a fishy or sour smell or taste after it's been thawed, or after about 24 hours of being stored it in the refrigerator.

What are the clumps in my breast milk? ›

“Fat globules” in milk are actually biofilm formation from bacteria, cholesterol/lipids in the milk, and general ductal debris (dead cells), usually in the setting of hyperlactation (oversupply) and dybiosis (imbalance of breastmilk microbiome).

Why does my fresh breast milk smell sour? ›

If your milk tastes/smells sour or rancid rather than soapy, the cause may be chemical oxidation rather than lipase (Mohrbacher, p. 461). Mom's intake of polyunsaturated fats may be involved, or free copper or iron ions in her water.

How do you use alcohol test strips for breast milk? ›

The strips are individually wrapped and contain a color panel on the back of each package. You dip the strip in milk for 2 mins then see if the milk is safe to give to baby. Easy to use and ease to read!

How do you test breast milk for alcohol strips? ›

Instructions. Just saturate the MilkScreen alcohol test strips with breast milk. If the test pad changes color at 2 minutes, alcohol is present (at or above 13.1 mg/dL).

Can you test the breast milk for infection? ›

Breast milk culture is not routinely required in primary care for women with mastitis. However, in women with lactational mastitis, send a sample of breast milk for microscopy, culture, and antibiotic sensitivity, if: Mastitis is severe or recurrent, or presentation is unusual. Hospital-acquired infection is likely.

How can you tell if your breast milk is fatty? ›

As your baby continues to nurse, they begin to pull milk from deeper within the breast where the fatty milk cells are stored. This milk, which is more fat-filled than the earlier milk, is called the hindmilk. Hindmilk often appears thick and creamy and is richer and more calorie dense than the foremilk.

Can your breast milk not have enough fat in it? ›

The composition of breast milk shows that fats make up to 3 to 5 percent of all the nutrients found in breast milk. These numbers change throughout the day and can be caused by a variety of factors. This can be from decreasing fat levels, how full your breasts are, and your baby's age.

Why doesn't my breast milk have a lot of fat? ›

The fuller the breast, the lower the fat content of the milk. Therefore, milk that is expressed at the beginning of a nursing or pumping session tends to be more watery than milk expressed at the end. (However, if sessions occur close together – and the breast doesn't have time to refill – this may not always be true.)

Why are you not supposed to shake breast milk? ›

Should I swirl or shake breast milk? Breast milk will separate because it is not homogenized, meaning the cream will rise to the top. Before feeding, gently swirl the container to mix the cream back through. Do not shake vigorously however as this breaks up the proteins which are so vital for baby's gut lining.

Can high lipase milk make baby sick? ›

Dr. Chang points out that while excess lipase can change the taste of the milk, it does not make it harmful to the baby. In fact, it may even have benefits for your milk.

Can you fix high lipase in breastmilk? ›

Mix it with freshly pumped milk or other foods

Combining soapy-smelling refrigerated milk with freshly pumped milk can sometimes sweeten the flavor again. Mixing stored milk with solid foods is only an option if your baby is already old enough to begin eating solids.

How long does it take for breast milk to spoil? ›

Freshly expressed or pumped milk can be stored: At room temperature (77°F or colder) for up to 4 hours. In the refrigerator for up to 4 days. In the freezer for about 6 months is best; up to 12 months is acceptable.

Is it normal for breastmilk to look curdled? ›

Babies' spit-up becomes curdled when milk from breastfeeding or formula mixes with the acidic stomach fluid. Time also plays a role here. Immediate spit-up after feeding will probably look like regular milk. If your little one spits up after some time as passed, it's more likely to look curdled milk.

What happens if baby drinks breast milk that sat out too long? ›

"One of the risks of breastmilk left out too long is growth of bacteria, which can't be detected on visual inspection." There isn't a specific appearance, for example, or color of milk that denotes it's "bad." But milk that's left out too long can result in vomiting or diarrhea in your baby, Dr.

How long before breast milk goes bad in bottle? ›

After 4 days of refrigeration, your breast milk should be used or thrown away. Breast milk has properties that slow the growth of bad bacteria. These properties begin to decline after a few days of refrigeration. If you think you won't use breast milk within a few days, the sooner you freeze it, the better.


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