How To Tell If Breast Milk Is Bad: Best Tips To Store, Defrost & Freeze

How To Tell If Breast Milk Is Bad

There are a lot of rules regarding breast milk. If you have frozen breast milk, stored breast milk, or plan to travel with breast milk, you need to know the signs that your breast milk has gone bad.

Storing breast milk takes some finesse, and there are rules that you need to follow if you plan to keep the milk that you have pumped or have been donated. Frozen milk is only good for a certain period and when kept at a certain temperature.

Even temperature fluctuations of just a few degrees over time can affect the quality of breast milk. And even breast milk that is frozen, when stored correctly, is only good for a certain amount of time.

This article will help you to understand how to store breast milk so that it won’t go bad. We will also discuss how to tell if breast milk is bad so that you don’t end up feeding your child expired breast milk.

Clear Signs Your Stored Breast Milk Has Gone Bad

The following are some signs to pay attention to determine if your breast milk has gone bad. While some babies can be sensitive to the breast milk that comes straight from the mother’s breast, you’ll only have to deal with spoiled breast milk if you’re storing breast milk after a pumping session.

1. It Has a Sour Taste

If your breast milk tastes sour, there’s a good chance that your expressed milk has gone bad. The only way to know for sure is to taste it. Like cow’s milk, human breast milk will go bad if not stored correctly.

Many things can affect the way a mother’s milk tastes, but if the thawed milk or fresh milk tastes sour, it’s probably gone bad and should not be given to the baby.

Many Things Affect the Taste of Breast Milk

Many things can affect the taste of a mother’s milk. While you don’t necessarily need to taste every bottle of your own pumped breast milk, it might be a good idea to try the thawed breast milk or freshly pumped milk any time you have a significant change to your diet, are on new medications or decide to thaw breast milk that has been stored in a deep freezer for a prolonged period.


The foods that you eat can affect the taste of your breast milk, especially if your diet has changed significantly. For example, if you don’t usually eat spicy food and then suddenly do, your breast milk may taste differently after. A mother’s diet can change the taste of breast milk a lot and the drinks that a mother consumes.

Changed taste due to a changed diet does not immediately indicate spoiled breast milk. However, if you don’t remember what you ate when you thaw stored milk, and it tastes odd or off to you or your baby, it may be a good idea to toss it. Most babies, however, don’t mind a slight change in taste due to diet changes, and it exposes your baby to different flavors.

No one likes dumping the liquid gold that is breast milk, but if it’s best for the baby’s health, it’s worth it.

How To Tell If Breast Milk Is Bad


If you have to begin taking a medication, first of all, be sure that you check with your doctor to be sure that you can breastfeed while on the medication. If you get the all-clear, be aware that your breast milk may taste different. If it is a short-term medication, you may want to label storage containers with the date (you should be doing this anyway) and the medication you are taking.

Spoiled Breast Milk Has a Very Distinct Sour Taste

Spoiled breast milk has a taste that cannot be mistaken. If you’ve ever neglected to check the expiration date on a gallon of regular cow’s milk and had a drink of spoiled milk, you know that sour milk has a taste you don’t mistake for something else. You know it when you taste it.

It’s rancid, rotten, and tastes awful and sour.

2. The Milk Smells Spoiled

When it comes to smell, you may find that the unmistakable smell of your breast milk may change depending upon a few factors. You may notice a soapy smell if you are smelling stored breast milk. This might occur because you aren’t smelling the milk in some cases, but the breast milk containers themselves.

People often clean the breast pump they use or the breast milk storage bottles or containers in scented soaps, and that smell will permeate even after the milk or container is frozen. To remedy this, be careful to rinse well when washing pump parts and containers.

Again, medications that you take may change the smell of your milk.

Also, the absence of lipase, which is an enzyme in breast milk, can make your breast milk smell. A high level or excess lipase activity can cause your milk to smell odd. Some have likened it to a fishy or metallic smell. Some babies will refuse to eat this, but you don’t have to discard it. Scalding breast milk will fix the issue.

How Your Nose Will Know It’s Bad

Bad breast milk will have a rancid smell to it. It will smell spoiled, funky, or sour. If you aren’t sure whether you can trust your nose, there’s no better way to tell from this point than to taste it.

3. It Doesn’t Mix Well

Your breast milk can change depending on how you store it. If you have refrigerated milk, you may notice that after a while, it separates. This is because the fat rises to the top and creates a plug or cap on the milk.

If the milk is still good, you can swirl the contents, and they will re-mix well. If you swirl the contents of the container, however, and there are chunks that remain, or the layers that have been created do not go back to just one fluid liquid, then the breast milk needs to be thrown away.

How Long is Freshly Pumped Milk Good For at Room Temperature?

If you use a breast pump to express breast milk, you may have wondered how long you can leave it sitting out at room temperature. Maybe you plan to use this freshly pumped breast milk in your next feeding sessions and don’t want to worry about storing it, freezing it, or cooling it first.

The following are the circumstances and lengths of time you can keep breast milk out for, depending upon where it has been after it has left the breast.

Room Temperature

Your breast milk leaves your body in a very warm state. It is close to your body temperature because it came from your body. So once you have freshly expressed milk, it immediately starts to cool down.

You can leave freshly expressed breast milk out at room temperature for up to 8 hours before it has to be discarded.

Previously Refrigerated

If you have breast milk in your refrigerator and want to warm it up by letting it sit out or pull it out of the fridge to take along with you during an outing, it needs to be consumed within four hours.

You can attempt to keep it cooler for longer by using an insulated cooler bag, but unless you can be sure that it’s stored properly at the temperature of your refrigerator, don’t stray from the four-hour rule. After four hours, discard or don’t feed the milk.

Frozen Breast Milk

There are a few different factors to consider when it comes to milk that has been stored in a freezer.

If you have breast milk that is thawed and was preciously frozen, it can stay out for four hours before you need to discard it. This is only if you have thawed but not warmed the milk.

Frozen milk that has been thawed and warmed up cannot sit at room temperature. It must be used immediately. If you let it sit out, you risk things like bacterial contamination, potentially making your baby ill.

How to Defrost Breast Milk

To safely defrost or thaw breast milk from a frozen state to a state that is ready to consume, below are a few methods that will keep you from worrying that you’ll spoil the milk.

1. Running Water

Under lukewarm running water, such as the kitchen sink, allows the breastmilk storage bag to thaw and warm. Test the temperature after a few minutes of not just the storage container and the milk itself to avoid serving your baby milk that is too cold or too warm.

Store breast milk, expressed breast milk

2. In the Refrigerator

Place the storage bottle with frozen milk in the fridge to naturally thaw, just like you would any other frozen food from the freezer. Remove it from the fridge when you’re ready to use the milk, and warm it under some warm running water.

3. A Bowl of Warm Water

If you typically store your milk from pumping sessions in bags, you can place the frozen bag in a bowl of warm water to thaw and warm it for the baby to consume.

Can you refreeze breast milk?

The CDC, or Center for Disease Control and Prevention, warns never to refreeze breast milk. Doing so is strictly against storage guidelines, and it can compromise the nutrients and the health of your baby. Like other foods, it is not safe to refreeze thawed breast milk. You wouldn’t want to eat meat that’s been thawed, frozen, and then thawed again.

How to Prevent Breast Milk from Going Bad

Sometimes you’re on a long trip or in a car for a long time. Or you lose power and cannot properly adhere to the storing guidelines that your milk requires. In such cases, we can’t keep breast milk at the right temperature for more than a few hours.

According to any medical professional, this milk that has not been appropriately stored needs to be disposed of. This doesn’t mean you have to dump it. You can still use it for milk baths, milk jewelry, homemade soap, or lotion. However, you cannot and should not feed it to your baby.

1. Use the Right Storage Containers

Using the correct containers to store your milk is very important. It would be best to have an airtight seal on the bag that you are keeping the milk in. Your best bet is to purchase bags to store your milk specific for breast milk pumping and storage.

2. Stick to the Rules

Note the times you are pulling milk from the freezer, the time you pumped, or the amount of time a bottle of milk has stayed out at room temperature. Stick to the rules regarding time limits.

3. Don’t Thaw More than You Need

No one wants to dump expressed milk. Pumping takes time and energy, and it can be hard work. Don’t thaw or prepare more milk than what you will realistically need for your baby at any given time. It may seem like a hassle, but thawing milk and warming it as required will waste far less milk due to spoilage than having to dump excess milk that was not consumed.

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