How Long Can Breast Milk Sit Out at Room Temperature?

Breast milk is precious, and there’s nothing more disappointing than pouring it down the drain. So it’s important to store it correctly.

Having a newborn comes with a steep learning curve — it can be difficult to remember all the crucial do’s and don’ts. But we’re here to help.

Moms often ask us how long breast milk can sit out or last when stored in the fridge or freezer. We’ll break down each breast milk storage situation to help you know exactly what to do to safely preserve your breast milk — without wasting a drop.

Storage Times for Breast Milk

If you’re storing your breast milk, the amount of time you can keep it depends on where and how you store it. Remember that the longer you store breast milk, the more vitamin C it loses ⁽¹⁾.

If you’re keeping your breast milk in the freezer, it can be stored for up to 12 months, although it’s best to use it within six months. Place it in the back of the freezer where it’s coldest.

You can store breast milk in the refrigerator for four days. Keep it in the coldest part of the fridge, at the back. If you think you may not use the milk, move it to the freezer within three days.

When you’re on the go, you may need to store the milk in an insulated breast milk cooler. If it contains ice packs and is chilled all the time, the milk can last up to 24 hours.

Any time you’re handling breast milk, ensure that your hands are freshly washed with soap and water.

How Long Can Breast Milk Sit Out at Room Temperature?

The biggest question you may have about storing and using your breast milk is how much time you can leave it out at room temperature. There will be times that you’ve pumped or thawed milk that your baby didn’t drink right away.

Here are the guidelines for keeping milk at room temperature, which is 77 degrees Fahrenheit or less:

• Freshly pumped milk: Can sit on the counter for up to four hours before it needs to be refrigerated or frozen.
• Refrigerated milk or frozen milk that has been thawed: Can sit on the counter for up to two hours before it should be discarded.
• Milk left in the bottle after a feeding: Should be finished by the baby within two hours, after which the remaining milk should be discarded.

You can feed your baby breast milk at room temperature or even a little below. It isn’t necessary to warm it, but some babies prefer it to be warm. If your little one likes warm milk, you can use a bottle warmer or place the bottle in warm water to heat the milk.

One thing you may notice when storing your milk is that it separates, with the fattier milk rising to the top of the container. This isn’t anything to worry about. Give it a little swirl to mix it back up again.

Thawing Frozen Breast Milk

When the time comes to use your expressed milk from the freezer, you need to thaw it safely. You should stick to a “first milk in, first milk out” rotation to use up the older bags of milk before they’re no longer viable ⁽²⁾.

You shouldn’t thaw breast milk in a microwave. This can create hot spots that may burn your baby’s mouth and throat. It could also destroy some of the nutrients in the milk.

The proper way to thaw the milk is to move it to the refrigerator overnight, not at room temperature. Another option is to hold it under lukewarm running water until it’s thawed. Or, you can place it in a basin of hot tap water until it’s thawed.

Once you thaw the milk, it can be kept in the refrigerator for up to 24 hours but should not be refrozen.

How to Store Breast Milk

At some point, you may need to pump some of your breast milk. Perhaps you’re going back to work or you want your partner to be able to feed the baby occasionally. It could also be that you have excess milk and don’t want to waste it.

Whatever your reasons, you need to know how to store your expressed milk.

There are three basic containers that you can store your breast milk in: glass, hard plastic, or breast milk storage bags. If you’re using hard plastic, make sure it’s BPA-free ⁽³⁾.

Plastic and glass containers should have a cap and not simply be covered with foil or cling wrap. The storage bags need to be specifically designed for storing breast milk. A regular sandwich or freezer bag is not suitable.

Breast milk bags are sometimes difficult to store on their own and can tear easily when unprotected in your fridge or freezer. I used to put the breast milk bags inside a hard plastic container to protect them.

Whatever container you store your milk in, make sure you label it. Write the date and time you expressed the milk on the container. If it’s going to a day care facility, you will also want to add your baby’s name.

Like most liquids, breast milk will expand when frozen. You don’t want to fill the containers full, or they may break as the milk freezes. Also, you should only put one feeding’s worth of milk in each container.

If you’re freezing the milk in breast milk bags, lay them flat in the freezer—they’re less bulky than if you set them upright. When they freeze flat, they’re easier to stack and store.

Editor's Note:

Michelle Roth, BA, IBCLC

FAQs

Can I Put Breast Milk Back In the Fridge After Baby Drinks From It?

Once a baby has drunk from a bottle of breast milk, it’s best not to put it back in the fridge for later use. Bacteria from the baby’s mouth can contaminate the milk, and it should be used within 1-2 hours after the baby first starts drinking it.

How Do I Know If My Baby Drank Spoiled Breast Milk?

If your baby drank spoiled breast milk, they might show signs of gastrointestinal discomfort, such as fussiness, vomiting, or diarrhea. If you worry your baby has consumed spoiled milk and shows any signs of distress, monitor them closely and consult your pediatrician.

Can I Combine Breast Milk From Two Different Days?

Yes, you can combine breast milk from two different days, but make sure both batches are cooled in the refrigerator before mixing.

Do not add warm, freshly pumped milk to already cooled milk. It’s also a good practice to use the oldest milk first and label bottles with dates to manage storage effectively.