For proper storage of breast milk, the US CDC recommends using the following storage and preparation techniques to keep expressed breast milk clean and safe for feeding infants later. These tips cover storing pumped or hand expressed breast milk at different temperatures in refrigerated units. 

This CDC chart creates a quick printable summary to reference each time you store milk.

The following factors determine how long expressed milk can be safely stored:

• Volume of milk (How much milk is expressed),
• Room temperature when milk is expressed,
• Temperature changes in the refrigerator or freezer,
• Cleanliness of the area where milk is stored

Short Summary

• Freshly pumped milk lasts up to 6-8 hours at room temperature (20-22 degrees C / 68-72 F)
• Stored refrigerated Breast Milk is good for 3-8 days (convenient for moms who travel and work away from home). After thawing, you must within 24 hours or less.
• Frozen Breast milk can lasts 6-8 months. 
• Breast milk in deep freeze can last up to 12 months

Detailed Guideline for Storing breast milk after expressing:

• Use breast milk storage bags or clean, food-grade containers to store expressed breast milk. Make sure the containers are made of glass or plastic and have tight fitting lids.
  
  - Avoid bottles with the recycle symbol number 7, which indicates that the container may be made of a BPA-containing plastic.
• Never store breast milk in disposable bottle liners or plastic bags that are not intended for storing breast milk.
• Freshly expressed or pumped milk can be stored:
  - At room temperature (77°F or colder) for up to 4 hours.
  - In the refrigerator for up to 4 days.
  - In the freezer for about 6 months is best; up to 12 months is acceptable. Although freezing keeps food safe almost indefinitely, recommended storage times are important to follow for best quality.

Detailed Expressed Milk Storage tips:

• Clearly label the breast milk with the date it was expressed.
• Do not store breast milk in the door of the refrigerator or freezer. This will help protect the breast milk from temperature changes from the door opening and closing.
• If you don’t think you will use freshly expressed breast milk within 4 days, freeze it right away. This will help to protect the quality of the breast milk.
• When freezing breast milk:
  - Store small amounts to avoid wasting milk that might not be finished. Store in 2 to 4 ounces or the amount offered at one feeding.
  - Leave about one inch of space at the top of the container because breast milk expands as it freezes.
• If you deliver breast milk to a child care provider, clearly label the container with the child’s name. Talk to your child care provider about any other requirements for labeling and storing breast milk.
• Breast milk can be stored in an insulated cooler with frozen ice packs for up to 24 hours when you are traveling. At your destination, use the milk right away, store it in the refrigerator, or freeze it.