Frequently Asked Questions

Why have I seen different recommendations for storing breast milk?

Many factors can affect how long breast milk can be stored in various locations, such as storage temperature, temperature fluctuations, and cleanliness while expressing and handling breast milk. These factors make it difficult to recommend exact times for storing breast milk in various locations.

Does the temperature of the room matter if I plan to leave breast milk on the counter until I use it?

Yes. If you live in a warmer climate or keep your home at a warmer temperature, you should 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.

What is the recommended method to store and serve breast milk that is leftover from a feeding?

If your baby did not finish the bottle, the 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 milk in smaller amounts.

See CDC’s Storage and Preparation of Breast Milk guidelines for more information.

How can I determine the temperature of my refrigerator and freezer?

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 thermometersexternal icon. Even if your refrigerator/freezer do show the temperatures, appliance thermometers may be important if you lose power or have mechanical problems.

If I move stored breast milk that has been in a kitchen freezer to a deep/chest freezer or vice versa, do the storage recommendations change?

No. You can count the age of the milk from the first time that it was frozen, regardless of when it was moved. As long as the temperature of the freezer is 0°F or below, it does not matter whether it is a kitchen freezer or a deep freezer. Breast milk can be stored in the freezer (at 0° F or colder) for up to 12 months, although using it within 6 months is best. The temperature of kitchen freezers is typically 0° F and although deep freezers or chest freezers may be able to operate at a temperature colder than 0° F, both types of freezers fall within the guideline of keeping frozen milk at a temperature of 0° F.

Moving frozen breast milk between freezer locations should be done quickly to ensure that the milk stays frozen. It may be useful to pack the frozen breast milk on ice packs while transporting the milk from one location to another.

If I don’t use breast milk stored in the refrigerator within a few days, can I still freeze it to use later?

After 4 days of refrigeration, your breast milk should be used or thrown away. Breast milk has properties that 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, the sooner you freeze it, the better.

Can I mix freshly expressed 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. It is also important to consider storage duration guidelines for breast milk. For example, if combining cooled milk pumped on different days, the duration of storage should be based on when the older milk was first stored.

The power went out! Do I have to throw out all of my stored frozen breast milk?

Your breast milk may still be safe, but it depends on how long the power is out and how defrosted or warm the breast milk becomes. Freezers, if left unopened and full during a power outage, will keep food safe for about 48 hours (about 24 hours if half full). When freezers are full, the other frozen items help keep the freezer colder longer. The refrigerator will keep food cold for about 4 hours if it is 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.

Where can I store my breast milk at work?

Expressed breast milk is a 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 health risks (sanitary or safety issues); however, it is important that the breast pump equipment be cleaned, dried, and stored in a sanitary (clean) environment to protect the equipment (and expressed breast milk) from contamination.

What are the recommendations for properly storing expressed breast milk while traveling?

Traveling by air?
  • You are allowed to 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)external icon has specific screening procedures for anyone traveling with breast milk.
  • Consider keeping a copy of the TSA regulations in your carry-on bag.

Expressed breast milk may be stored and transported in an insulated cooler bag with frozen ice packs for up to 24 hours, or else frozen in dry ice (follow safety precautions when handling dry iceexternal icon). Once breast milk is cooled, it should remain cool until it is consumed. Breast milk that has been transported in an insulated cooler bag with frozen ice packs can then be refrigerated or frozen.

Depending on the destination, if no reliable breast milk storage is available, a mother traveling with expressed breast milk could consider using temperature-controlled shipping to transport breast milk or discarding her expressed breast milk. Continuing to express breast milk regularly will help a mother to maintain her breast milk supply until she and her nursing infant or child can be reunited. Visit CDC’s Travel Recommendations for the Nursing Mother webpage to learn more.