How Long Can You Leave Breastmilk Out?

Claire Dowell
June 14, 2021

Pumping and breastfeeding are hard work! Once you’ve made this magic, it would be truly tragic to see it go to waste. The rules about different foods being left out, frozen, and refrozen can be confusing, and breast milk is no different. It’s important to know the proper procedure for breastmilk storage so that it stays fresh and healthy to help your baby grow strong!

How long can breast milk be left out … ?

When thinking about leaving breast milk out, we like to remember the 4/4 rule. The CDC guidelines recommend that freshly expressed breast milk not be left out for longer than four hours at room temperature, or longer than four days in the refrigerator. If it exceeds this amount of time, there’s a likelihood that bacteria could grow in it. When it comes to feeding babies it is always best to be on the safe side and stay below 4 hours or 4 days. If you’re not anticipating the milk will be consumed within this time period, freezing it is best. Breast milk can be frozen for up to twelve months, but it is best to use it within six months.

How should breast milk be stored … ?

Whether you are storing your milk in the fridge or freezer, using breast milk bags or tightly sealed food containers is best. Here is one of our favorite storage brands Lansinoh! It is recommended to avoid plastics labeled with the number 7 as they can contain BPA which may be harmful when ingested. Once you have chosen the right container for your milk, labeling is super important. You should label with the date and time the milk was expressed so that you won’t have any mix ups about whether or not it is safe to consume. Try to keep your breast milk stored on a stable shelf in the back of the fridge or freezer to make sure that the temperature doesn’t fluctuate too much.

My milk is frozen, now what …?

Once you’re ready to use the breast milk, removing it from the freezer to thaw is the first step. Remember, once breast milk is thawed, it cannot be refrozen and should be either consumed or thrown away. To thaw your milk, it’s recommended to refrigerate overnight or run under lukewarm water until thawed. Avoid the use of a microwave which can destroy those key nutrients and has the potential to injure your baby if it is too hot. Once the milk is at room temperature, it should be drunk within two hours.

Pro tips!

  • Breast milk expands when it is frozen, so leave about an inch of extra space between the milk and the lid of your container to avoid any messes!
  • When storing your milk, try to remove all the air bubbles you can. This helps prevent freezer burn on the milk and gassiness in your baby!
  • Try laying your milk bags flat to freeze, as it helps maximize the amount you can store. Some people suggest using a cookie sheet to freeze them initially so they can lay flat, then stacking the bags on top of each other.
  • Room temperature is typically 77 ℉
  • To make sure your milk is brought to the right temperature for drinking, test a few drops on a sensitive area of your skin, such as the inside of your wrist.
  • Keep a reminder of the guidelines on your fridge! If you print out our graphic and hang it up, it’ll make it much easier for babysitters or other family members to remind themselves of the proper safety tips!

Graphic by Kaylah Nicholson


  1. Centers for Disease Control and Prevention. (2021, February 12). Proper Storage and Preparation of Breast Milk. Centers for Disease Control and Prevention.