Everything you need to know about breastmilk storage

Like breastfeeding, storing breastmilk can be a bit tricky. From freezing it to how long it can sit out, here’s everything you need to know about breastmilk storage. 

There’s no reason to cry over spilled milk, but there are plenty of reasons to cry over breastmilk that wasn’t stored properly. Not only did you work hard to pump that liquid gold but sour milk can also make your baby sick. Here are the basics when it comes to storing breastmilk safely.

How long can breastmilk sit out at room temperature?

The rule of thumb is that untouched breastmilk is safe for your baby if it’s been sitting at room temperature for four hours or less, advises Deborah Campbell, a neonatologist at The Children’s Hospital at Montefiore in the Bronx, New York. If it’s been longer than four hours, you need to throw it out (sorry!). If you know you’re not going to use the milk during that time and your baby hasn’t sipped from it yet, just stick it in the fridge.

How long can breastmilk stay in the fridge?

According to the American Academy of Pediatrics, once you’ve put breastmilk in the refrigerator, it can stay there for up to eight days. However, it’s best to use the milk within the first four days because that’s when its fat, digestive enzyme activity and anti-infection benefits are at their peak, says Campbell. To keep the milk cold, be sure to store it on the bottom shelf at the back of the fridge, not in the door.

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How long will breastmilk keep in an insulated cooler?

If you are hitting the road and need to bring along a bottle or bag of breastmilk, you can pack it in an insulated cooler with an ice pack and it should be safe for up to 24 hours.

How long will breastmilk keep in the freezer?

If you don’t plan on using the milk within the four days that it’s at its best in the fridge, you should freeze it within 24 hours of pumping. Breastmilk is good for nine months when stored in a freezer attached to a refrigerator. As with storing it in the fridge, the milk should be kept in the back of the freezer. If you have a deep freezer or chest freezer, you can freeze the milk for up to one year.

How do I freeze breastmilk?

Breastmilk freezer bags are your best storage option. Choose two- or four-ounce storage bags and leave a little room at the top of the bag because the milk will expand when it freezes. Make sure to write the date pumped on the bag so you’ll know when to throw it out. Don’t use disposable bottle liners or other types of plastic bags. If you’re afraid that the bags may tear, you can put them inside a plastic container with a lid. You should avoid any containers made with bisphenol A or S, but you can freeze breastmilk in glass or BPA-free plastic containers. Wash all bottles with hot, soapy water beforehand (or in the dishwasher) and dry them well. Do not use chemical disinfectants.

How do I thaw breastmilk safely?

There are several ways to thaw your breastmilk.
-Place it in the fridge overnight to thaw.
-Run the bottle under warm water.
-Set the bottle in a container of warm water.
-Use a waterless bottle warmer.
Whichever method you choose, keep in mind that slower thawing means less fat loss. When you thaw the milk too quickly, it causes it to lose antibodies. Whatever you do, do not thaw your breastmilk in a microwave oven because it can thaw the milk unevenly and potentially burn your baby!

Why does thawed breastmilk smell and look different than fresh breastmilk?

That’s normal. This happens when women produce breastmilk that is high in an enzyme called lipase. While this enzyme helps digest the fat content in breastmilk, it can also affect the smell and taste of both fresh and frozen milk (it usually makes it smell and taste metallic or soapy). Women often don’t realize that their breastmilk is high in lipase until they freeze it because the changes to the milk take a few hours—or even a day—to take effect, so you probably wouldn’t notice the changes with fresh milk. If you’re concerned about your baby not wanting to drink the breastmilk, talk to your doctor to find out about a process to help neutralize the enzyme and lessen the smell.

How do I know if my breastmilk has gone bad?

Generally speaking, you’ll know that your breastmilk has gone bad if it smells rancid or sour. You probably notice that your breastmilk will separate naturally after you pump, with the fat rising to the top. “When milk is still good, it mixes back together easily with a gentle swirl of the bottle,” says Campbell. If your milk doesn’t do this or has chunks floating in it, throw out the milk, adds Campbell.

How do I warm a bottle of breastmilk safely?

Warming breastmilk that has already been thawed is best done in lukewarm water (usually 40°C/104°F) for about 20 minutes. Some babies prefer their milk cooler, while others like it fully warmed. As you get to know your baby’s preferences, you can adjust your warming times. As with thawing, never use a microwave oven to warm breastmilk as it can heat the milk unevenly and scald your little one.

Can I reheat a bottle of breastmilk?

We all know how precious breastmilk is, and the thought of wasting even a drop makes us cringe. But once a baby starts drinking a bottle of milk, some bacterial contamination occurs in the milk from the infant’s mouth, says Campbell. This means that you shouldn’t reheat the milk. A bottle that your baby has drank from is only good for about an hour, says Campbell. She recommends storing milk in smaller bottles so that your baby uses the full portion at each feeding and you don’t have to fret over throwing out your precious liquid gold.

Read more:
6 magical ways that breastmilk changes to meet your baby’s needs
How to get your baby to take a bottle