Storing and reusing Breast Milk


Based on the Ministry of Health guidelines for storing breast milk


  • You should wash your hands before you express breast milk.
  • Store breast milk in an airtight storage container. Unimom milk storage bags or bottles.
  • Milk should be stored in small portions to prevent waste – around 100–300 mL.
  • Date containers at the time of collection, and make sure caregivers use the oldest milk first.
  • Fresh or refrigerated milk retains beneficial properties and is preferable to breast milk that has been frozen.
  • If refrigerating or freezing breast milk, store it in a new container rather than adding it to previously refrigerated or frozen milk.
    • Adding expressed breast milk to frozen milk can cause the milk to thaw and then refreeze, which increases the risk of bacterial growth in the milk.
  • Wash containers and feeding equipment in hot soapy water, and then rinse.
  • If the infant is three months old or younger, the containers and equipment also need to be sterilised. See our "Cleaning and Sterilising options"
  • When refrigerating, expressed breast milk should be stored in the bottom half of the fridge, at the back. Fridges should operate at 2–4 °C.
  • If you only need to store breast milk a short time, and don’t have access to a fridge or freezer, you can use an insulated cooler bag with ice packs. See our transport kits
    • Don’t use this method to store milk for more than 24 hours.
    • The ice packs should be in contact with the milk containers at all times.
    • Try not to open and close the cooler bag too often.

Note that these guidelines are for expressed breast milk that is fed to healthy, full-term infants who live at home.

 Guidelines for storing expressed breast milk

Storage conditions

Storage time


Room temperature
(< 26ºC)

4 hours

Cover containers and keep them as cool as possible (eg, surround the closed container with a cool towel to help to keep the milk cooler)


48 hours

Store milk in the back of the main body of the fridge


Freezer box in refrigerator


2 weeks

Store milk toward the back of the freezer, where the temperature is most constant

Separate door fridge/freezer

3–6 months

Separate deep-freeze

6–12 months


Using expressed breast milk

  • Frozen expressed breast milk can be thawed in the refrigerator or by placing the container in warm water until the milk has thawed.
  • Expressed breast milk should NOT be thawed or heated using a microwave because: 
    • microwaving destroys some of the milk’s immunological components
    • there is a risk of uneven heating and scalding.
  • Expressed breast milk can be warmed by placing the cup or bottle containing the milk in hot water.
    • Before feeding the infant, caregivers should swirl the container of milk to mix the fat portion back in and distribute the heat evenly.
    • They should test the temperature of the milk by shaking a few drops on the inside of their wrist. It should feel comfortably warm to the touch before being given to the infant. Alternatively use our Thermal Sensor storage bags
    • Do not shake breast milk but swirl. Because shaking expressed milk (or boiling or freezing it) denatures the shaped molecules of the protective proteins, leaving only the pieces - the amino acids - the parts. Lactoferrin, lysozyme, and other protective components work their protection magic when they are in their original shaped molecular structure. Some components remain intact, even during freezing, shaking or heating. They not only protect the gut from many kinds of infection, but also prevent inflammation of the gut lining. Even broken up, the separate amino acids are still really good stuff and are digested by the baby as nutrients.Cellular components are also susceptible to damage by physical stress. After all, they are living cells.