Your guide to safely storing breast milk

Breast milk provides important vitamins, nutrients and immunity for your little one – every drop counts. Knowing how to safely store breast milk can prevent your supply from spoiling or going to waste.

Dawn Schindler, RN, BSN, IBCLC, a lactation consultant at the Level IV Neonatal Intensive Care Unit (NICU) at Children's Health℠, answers commonly asked questions about how to store expressed (pumped) breast milk.

What is the best way to store breast milk?

Breast milk can be stored in any clean container with a lid including:

• Breast milk storage bags (preferred over regular snack or sandwich bags)

• Glass or plastic bottles with caps

Schindler recommends that you label each breast milk container with:

• The date and time

• The amount

"Don't rely on the bags to measure the volume of your milk accurately. It's more accurate to use the measurement in the bottle you pumped into and write that on the bag or container," Schindler says.

If your baby goes to daycare, or is being cared for in a hospital, you may need to have more information on each container, including:

• Your baby's name and date of birth

• The mother's name and date of birth

• The time and date of pumped milk

• Any prescription or over-the-counter medication the mother took

How long can I store breast milk?

The Centers for Disease Control and Prevention (CDC) recommends storing breast milk in the refrigerator for up to four days and in a deep freezer for 6-12 months.

Find a place in the back of the refrigerator where it's colder and has less of a chance of getting knocked over. In the deep freezer, it's helpful to keep all breast milk together so it's easy to find. Wherever you store it, organize milk with the oldest in front to make sure you use it before it expires.

One tip Schindler recommends to all moms who want to freeze their breast milk is to freeze milk in the volume your baby is taking in. "Don't put 8 ounces in a bag if your baby is only drinking 4 ounces at a time," she explained. "This helps make sure you thaw the right amount and avoid wasting milk."

How long can fresh pumped breast milk stay out?

Fresh pumped breast milk can stay out at room temperature for about four hours before it is fed to your baby or put in the refrigerator. Schindler suggests you make a note about what time you pumped so you don't forget how long it's been out.

Can I mix breast milk from different pumping sessions?

Yes, you can combine and store breast milk from different pumping sessions.

Schindler recommends mixing breast milk that's been in the fridge and is cold. "You can store it in a few bottles in the fridge and once it's all the same temperature, you can combine it in one bottle or a bag. Then label it with the time and date of the first (older) pumping session," she said.

Can I refrigerate breast milk after feeding?

According to the CDC, after you feed your baby, it's safe to store any leftover milk in the same bottle you used for feeding in your fridge for an additional two hours. After that, it's best to toss leftover milk – to avoid the risk of bacteria growing in the nipple of the bottle.

How can I safely defrost milk?

Start defrosting frozen milk by placing it in the refrigerator. After there are no more chunks or ice crystals in the milk, it's considered thawed. Defrosting frozen milk in the fridge can take several hours or even up to a day.

After it's thawed, you can keep it in the refrigerator for 24 hours.

If you need to defrost milk more quickly, you can thaw it in a bowl of lukewarm water. Once the milk has turned into liquid, you can warm the appropriate amount for feeding and refrigerate what you don't use for up to 24 hours.

What does safe-to-use, thawed breast milk look like?

After it's thawed, you may notice that the fatty part of the breast milk is separated from the liquid part and looks like little white chunks. You may also notice that the liquid part looks more yellow than white.

To combine any separated parts, simply swirl the milk around.

What if my breast milk smells after defrosting?

The food we eat and the enzymes in our body can change the smell of breast milk.

"Most of the time, babies don't notice a small change in taste or smell," Schindler says. "If your baby refuses defrosted milk, try mixing it with freshly expressed milk."

If you continue to notice a different smell, talk to your baby's pediatrician or with a lactation consultant.

How will I know if my breast milk is spoiled?

Spoiled breast milk smells sour or fishy, similar to spoiled cow's milk. If you smell it and recoil, it's probably gone bad.

Can babies get sick from old breast milk?

If your baby has had spoiled breast milk, they'll likely let you know. They may throw up, or have an upset stomach, diarrhea or fever. It's important to call your pediatrician if you think your baby may be sick from having spoiled breast milk.

Do I have to warm up breast milk before feeding?

Newborns tend to prefer warmed milk. But as babies get older, they may be fine with cooler or room temperature milk.

If your child prefers warm breast milk, you can warm milk in a cup or bowl of warm water.

How can I safely transport expressed breast milk?

When you need to travel with breast milk, follow these guidelines:

• Place all the milk you need in a cooler packed tightly with ice or ice packs.

• Keep the cooler closed unless you need to get milk out.

• Keep it in a cooler, on ice, for up to 24 hours.

Learn more

Through our highly trained lactation consultants and Pediatric Milk Lab, Children's Health is dedicated to supporting breastfeeding moms in as many ways as possible.