Storing Breast Milk 101

If you're wondering how to safely and securely store breast milk, we've got you covered with everything you need to know.

You may have heard breast milk referred to as "liquid gold" for babies due to the steady supply of nutrients found within. Breast milk contains 87% water, 7% lactose, 4% fat, and 1% protein, and 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 breast milk improperly can degrade those important properties. We turned to the experts to learn more about how to safely and securely store breast milk so that your baby gets every ounce of its benefits.

Breast milk stored in fridge
Getty Images / Jamie Grill.

Where Should I Store Breast Milk?

Breast milk can be stored at different temperatures for different amounts of time, meaning that it's okay to keep breast milk out on the counter—for a little while, anyway. Human milk contains antibodies that are capable of killing many bacteria and viruses, unlike the cow's milk you buy from the grocery store.

The Centers for Disease Control and Prevention (CDC) offers the following guidance for where to store breast milk—and for how long:

Breast Milk Storage Guidelines

Countertop (rooms 77°F & colder): Up to 4 hours for freshly expressed milk; 1-2 hours for previously frozen milk


Fridge: Up to 4 days for freshly expressed milk; 1 day for previously frozen milk


Freezer: Within 6 months is ideal, but no longer than 12 months; never re-freeze breast milk after it's been thawed

When it comes to putting breast milk in the fridge or freezer, experts advise not to put it in the door area, but rather as far back as you can. "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, RN, 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. As for unfinished bottles of breast milk, be sure to use the rest within two hours after your baby's feeding; any extra should be discarded.

Tips for Safely Storing 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," suggests Hightower. "Sometimes your baby will need only two ounces, so there's no need to defrost a larger amount."

Never mix warm with cold

Mixing freshly expressed breast milk with older, cooled, or frozen milk from the fridge or freezer is not advised. 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 At Once?

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 six ounces per feeding, put six 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 little one's growth spurts slow down or when you've begun to introduce solids.

How to Thaw Frozen Breast Milk

If you have more than one bottle of breast milk currently frozen, be sure to thaw the oldest bottle first. You can thaw breast milk in a variety of ways, including:

  • Leaving it in the refrigerator overnight
  • Running it beneath a stream of lukewarm water from your faucet
  • Submerging the bottle in a pot of lukewarm water

Never use a microwave to thaw breast milk. You could potentially burn your baby's mouth, and microwaving breast milk also breaks down nutrients, making it less beneficial for your little one.

If you choose to thaw your breast milk in the fridge, be sure to use it within 24 hours of it becoming thawed. Once the breast milk is brought to room temperature, be sure to give it to your baby within two hours.

If you find yourself with lingering questions about storing, freezing, or thawing breast milk, be sure to reach out to a pediatrician, lactation consultant, or health care provider.

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Sources
Parents uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Boquien CY. Human milk: an ideal food for nutrition of preterm newbornFront Pediatr. 2018;6:295. DOI: 10.3389/fped.2018.00295

  2. American Academy of Pediatrics. Breastfeeding Benefits Your Baby’s Immune System.

  3. CDC. Proper Storage and Preparation of Breast Milk.

  4. American Academy of Pediatrics. Tips for Freezing & Refrigerating Breast Milk.

  5. CDC. Breastfeeding: Frequently Asked Questions

  6. American Academy of Pediatrics. Working Together: Breastfeeding and Solid Foods.

  7. WIC Breastfeeding Support. Storing and Thawing Breast Milk.

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