How to Store Breast Milk

There's a good reason why breastmilk is often referred to as liquid gold; it is chock-full of nutrients and antibodies that babies need. Studies show that breast milk is the perfect food because it contains 87% water, 7% lactose, 4% fat, and 1% protein. But it also has growth factors, antibodies, good bacteria for gut health, vitamins, minerals, enzymes, and much more. It's no wonder that parents worry about proper milk storage, especially those who rely on pumping to keep an ample amount on hand for their baby while they work.

But storing that milk improperly can degrade those important properties. Here's what you need to know to keep your liquid gold, well, golden.

Where Should I Store Breast Milk?

It's hard to believe that milk can stay out of the refrigerator and not go bad, but when it comes to breast milk, it's true. That's because human milk contains antibodies that are capable of killing many bacteria and viruses.

If you're storing for longer than a few hours, put the breast milk in a refrigerator or freezer instead. But never keep it in the fridge or freezer door. "It's better to keep it in the back, so it's less exposed to the changing temperature of the door opening and closing," says Kelly A. Hightower, R.N., a certified lactation counselor.

Those without access to a fridge—whether it's because of work, travel, or another reason—can store milk in an insulated cooler with ice packs, which will keep the milk safe for up to 24 hours.

How to Store Breast Milk

You can safely and easily store breast milk in the fridge or freezer. Here is what you'll need for supplies, as well as some safety tips to keep your milk as fresh as possible.

Supplies for storing milk

If you're planning to store breast milk in the fridge or freezer, stock up on the following supplies to help make your pumping and storing as easy as possible.

• Screw caps
• Hard plastic cups or bottles with tight lids
• Pre-sterilized breast milk storage bags
• Permanent markers or stickers to label bags with date and time
• An easily accessible section of fridge or freezer space to organize bags of milk

Secure your breast milk

Ensure the bottles or bags are closed tightly and securely to prevent leakage or spoilage. "Most breast milk storage containers allow up to five ounces, but it's a good idea to have some that contain less. Sometimes your baby will need only two ounces, so there's no need to defrost a larger amount," says Hightower.

Never mix warm with cold

According to the Centers for Disease Control and Prevention (CDC), mixing freshly expressed breast milk with older, cooled, or frozen milk from the fridge or freezer is not advised. Mixing fresh breast milk with older breast milk may be beneficial because it will level out nutrients from differing pumping times, but the CDC notes that the warmer temperature of freshly expressed milk should always be cooled first before mixing to avoid bacterial growth in the colder milk you're trying to store.

How Much Breast Milk Should I store?

It's easiest to store your breast milk in amounts you use at each feeding to avoid wasting it. For example, if your baby consumes 6 ounces in a feeding, put 6 ounces of breast milk in the storage container. It may also be helpful to have a few bags with smaller amounts of milk for times when your baby may not be ready for a full feeding, such as when your baby's growth spurts slow down or when you've begun to introduce solids.

How Long Does Breast Milk Last?

Write the date on the bottles or bags so that you can be sure not to use any expired milk. The general rule is that breast milk can be stored:

• At room temperature (less than 77 degrees F) for 4 to 8 hours
• At the back of a refrigerator for 3 to 8 days
• At the back of a freezer for up to 3 months

If you have defrosted breast milk in your refrigerator, Hightower recommends using it within 24 to 48 hours. And if you've got a deep freezer, your breast milk can likely last up to a year. "It's not that your milk will go bad and make your baby ill if it's in the freezer longer. But its nutritional qualities will be diminished," Hightower says.