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Heating expressed breast milk

When you are expressing, the breast milk you express should be chilled or frozen as quickly as possible.

Follow these guidelines for defrosting and warming up expressed breast milk.

Defrosting frozen breast milk

Follow these guidelines for defrosting breast milk when you remove it from a freezer:

  • Breast milk can be defrosted in the fridge, normally in around 12 hours.
  • You can also hold the bottle or bag of frozen milk under warm running water (a maximum of 37 degrees Celsius or 99 degrees Fahrenheit).
  • Once fully thawed, previously frozen breast milk may be kept at room temperature for a maximum of 2 hours - or in the fridge for up to 24 hours.

Thawed breast milk left at room temperature should be fed to your baby within 2 hours or thrown away.


Never re-freeze breast milk once thawed.

Freshly-expressed warm milk should not be added to already cooled or frozen milk, to prevent rewarming of the already-stored milk. It is best to cool down the newly-expressed milk first before adding it to older stored milk.

Warming breast milk

Healthy, full-term babies can drink breast milk at room temperature or warmed to body temperature.

Some healthy full-term and older babies can drink chilled milk when it is removed directly from the fridge. This is considered the safest choice.

To warm your milk, place the breast milk bottle or bag into a cup, jug or bowl of lukewarm water for a few minutes to bring it to body temperature (37 degrees Celsius or 99 degrees Fahrenheit). Alternatively, use a bottle warmer.

Do not allow the temperature to go above 40 degrees Celsius (104 degrees Fahrenheit).


Do not heat breast milk in a microwave or saucepan. Heating breast milk until it is hot can destroy some of the good properties in the milk.

Using a microwave to heat any fluids for your baby can lead to uneven heating. These hot spots can scald your baby's mouth.

If milk has separated

You may notice that the milk has separated into layers, with the creamier content at the top.

It's better to swirl the milk in the container to mix the layers again rather than shaking the container. Shaking the container may damage some of the proteins and other components of the milk.

Page last reviewed: 25 April 2022
Next review due: 25 April 2025