How Long Can Breast Milk Sit Out Before It Needs to Be Refrigerated?

Medically Reviewed on 6/9/2022
how long can breast milk stay out
You can let freshly expressed breast milk sit out for up to 4 hours at room temperature before needing to store it in the fridge or freezer.

According to research, freshly expressed breast milk stored in a closed container can be kept at room temperature for up to 8 hours if the outside temperature does not exceed 78.8 F.

The following are some common timelines for storing breast milk.

  • Room temperature: If the temperature is more than 78.8 F, freshly expressed breast milk can be kept at room temperature for up to 4 hours.
  • Insulated cooler: With ice packs inside, breast milk can be kept for 1 day.
  • Refrigerator: Breast milk can be stored in the fridge for up to 4 days.
    • If you are not going to use refrigerated breast milk within four days of pumping, freeze it as soon as possible.
  • Freezer: Breast milk can be kept in the freezer for up to 6 months. Place them in the back of the freezer, where the temperature is the most stable.
    • Milk stored at 32 F or colder is safe for longer periods, but the quality of the milk may suffer.
    • When the temperature is below 32 F, breast milk can be stored for up to 12 months. However, frozen milk should be used within 6 months.

Please note the following concerning breast milk storage:

  • When possible, babies who have been separated from their mothers should be given refrigerated milk rather than frozen milk.
  • When milk is frozen, some of its anti-infective properties are lost, but frozen milk still protects babies from many diseases and is far superior to commercial infant formula.

If you follow these guidelines, your milk will most likely be safe. However, before feeding your baby, you can always conduct a taste test. If the milk is sour, it has spoiled and must be discarded. Research indicates that the longer you store breast milk, whether in the fridge or freezer, the more vitamin C is lost. Remember to mark each batch of breast milk with the date it was expressed, so you know when it is okay to use it.

How can I store breast milk?

Depending on the temperature and accessibility, make sure to store breast milk in food-grade bags or bottles. It is best to express breast milk directly into a sterile plastic container, but you can store it in a clean, closed container or a special breast milk storage bag. It is good practice to keep the milk in small quantities.

Here are some breast milk storage guidelines to keep in mind:


  • Make use of glass or hard-sided plastic containers with tight-fitting lids.
  • Avoid containers containing the chemical, bisphenol A (BPA), which is denoted by a number three or seven in the recycling symbol.
    • A safe alternative is polypropylene, which is soft and semi-cloudy and has the number five in the recycling symbol or the letters PP or both.
    • You can completely avoid the risks associated with plastic by using glass.
  • Use containers that have been washed in hot, soapy water, rinsed thoroughly, and air-dried before use or washed and dried in a dishwasher.
  • Do not fill containers to the top and leave room for the milk to expand as it freezes.


  • Use freezer milk bags made specifically for storing human milk.
  • Place the storage bags in another container at the back of the refrigerator shelf or freezer, where the temperature will be most consistently cold.

It is not advisable to use disposable bottle liners or plastic kitchen or snack bags. Contamination is more likely with these. These bags are less durable and leak more frequently and certain types of plastic may destroy nutrients in milk.

How should I heat my breast milk?

Human milk should only be gently heated to retain as many vitamins and essential fatty acids as possible. This can be done in a separate bottle warmer that does not get hotter than 98.6 F.

Important considerations when warming and defrosting breast milk include:

  • Breast milk should not be heated in the microwave or a pan directly on the stove.
  • Warm milk promotes the growth of germs, which as a result, should be consumed right away.
  • Defrost frozen breast milk overnight in the fridge or under warm water.
    • Allowing the milk to defrost at room temperature is not recommended.
  • After warming breast milk, use it within two hours, and after the baby has finished feeding, discard any leftover milk.
    • Breast milk that has been thawed should never be refrozen.
  • According to research, it is recommended to reheat partially consumed breast milk only once because reheating would destroy the good bacteria and nutrients found in the milk.


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Medically Reviewed on 6/9/2022
Centers for Disease Control and Prevention. "Proper Storage and Preparation of Breast Milk." <>.

Office on Women's Health. "Pumping and Storing Breast Milk." <>.

WIC Breastfeeding Support. "Storing and Thawing Breast Milk." <>.