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Breast Milk Storage Questions and Answers

At a glance

Following recommended storage and preparation techniques can maintain the safety and quality of expressed breast milk for the health of your baby. Learn answers to frequently asked questions here.

Why do I see different breast milk storage recommendations?

Many factors can affect how long and where breast milk can be stored. These factors include storage temperature, rising and falling of the temperature, and cleanliness while expressing and handling breast milk. Therefore, it is difficult to recommend exact times for storing breast milk in various locations.

Does the temperature of the room matter?

Yes, if you plan to leave your breast milk on the counter until you use it. This is especially important if you live in a warmer climate or keep your home at a warmer temperature. Place breast milk in the refrigerator if it will not be used within a few hours. Breast milk does not spoil as quickly at cooler temperatures.

How do I store and serve leftover breast milk?

Leftover breast milk can still be used within 2 hours after the baby is finished feeding. After 2 hours, leftover breast milk should be thrown away. To avoid wasting unfed milk, consider storing, thawing, and warming it in smaller amounts.

See Breast Milk Storage and Preparation for more information.

How can I find the refrigerator and freezer temperature?

Your refrigerator should be 40°F or below, and your freezer should be 0°F or below. If your refrigerator/freezer thermostats do not show the temperatures, use inexpensive, freestanding appliance thermometers. Even if your refrigerator/freezer do show the temperatures, appliance thermometers may be important if you lose power or have mechanical problems.

Can I move frozen breast milk to another freezer?

As long as the temperature of the freezer is 0°F or below, the type of freezer does not matter. The temperature of kitchen freezers is typically 0° F. Deep freezers and chest freezers may be colder than 0°F. Breast milk can be stored at 0° F or colder for up to 12 months, although using it within 6 months is best. Count the age of the milk from the first time it was frozen, regardless of when it was moved.

Moving frozen breast milk between freezer locations should be done quickly to ensure that the milk stays frozen. Pack frozen breast milk on ice packs when moving it from one location to another.

Can I refrigerate breast milk and then freeze it later?

After 4 days of refrigeration, your breast milk should be used or thrown away. Breast milk properties slow the growth of bad bacteria. These properties begin to decline after a few days of refrigeration. If you think you won't use breast milk within a few days, freeze it as quickly as possible.

Can I mix fresh breast milk with older breast milk?

Mixing freshly expressed breast milk with already cooled or frozen milk is not advised because it can rewarm the older stored milk. It is best to cool freshly expressed milk before combining it with older, previously cooled or frozen milk. Also consider storage duration guidelines for breast milk. For example, if combining cooled milk pumped on different days, base the duration of storage on when the older milk was first stored.

The power went out! Do I throw out my frozen breast milk?

It depends on how long the power is out and how defrosted or warm the breast milk becomes. Freezers, if full and left unopened during a power outage, will keep food safe for about 48 hours. If the freezer is half full, they will keep food safe for about 24 hours.

The refrigerator will keep food cold for about 4 hours if it is left unopened. While the power is out, keep the freezer and refrigerator doors closed as much as possible.

Once the power is back on, check the condition of your stored breast milk. Frozen breast milk that has started to thaw but still contains ice crystals can be refrozen. If your breast milk has completely thawed but still feels cold, put it in the refrigerator and use it within the next day or throw it away.

Learn about infant feeding considerations during evacuations, power outages, and emergencies that impact safe water.

Where can I store my breast milk at work?

Expressed breast milk is food and may be stored alongside other foods in any refrigerator that is appropriate for food storage. Employers, coworkers, cleaning staff, other family members, and childcare providers should not consider or treat breast milk as a biohazard. Storing breast milk in a shared refrigerator and washing pump parts in community break rooms are unlikely to pose sanitation or safety health risks. However, it is important that the breast pump equipment be cleaned, dried, and stored in a clean environment to protect the equipment and expressed breast milk from contamination.

Learn more about breastfeeding and returning to your workplace.

How do I store expressed breast milk while traveling?

Expressed breast milk may be stored and transported in an insulated cooler bag with frozen ice packs for up to 24 hours. Or the milk can be frozen in dry ice following these safety precautions.

Once breast milk is cooled, keep it cool until it is used. Breast milk that has been transported in an insulated cooler bag with frozen ice packs can be refrigerated or frozen. Breast milk frozen with dry ice can be transferred to the freezer or to the refrigerator if you plan to use it in the next few days.

Depending on the destination, if no reliable breast milk storage is available, consider using temperature-controlled shipping to transport breast milk. If this is not an option, discard the expressed breast milk. Continuing to express breast milk regularly will help a mother maintain her breast milk supply until she and her nursing infant or child can be reunited. Visit CDC's Travel Recommendations for the Nursing Families webpage to learn more.

Traveling by air?‎

You can carry more than 3.4 ounces of breast milk in your carry-on bag, as well as ice and gel packs.

The Transportation Security Administration (TSA) has specific screening procedures for anyone traveling with breast milk.

Consider keeping a copy of the TSA regulations in your carry-on bag.