Safely Warm Cold Milk And Thaw Frozen Milk

While practicing safe storage of expressed breast milk is very important, warming and reheating refrigerated or frozen breast milk is equally important. Knowing these safety tips will help you get it right every time.

mom breastfeeding a newborn

How to warm breast milk

Warming frozen breast milk

  • Remove frozen milk from the freezer and place it in the refrigerator overnight or hold it under cool running water until thawed.
  • Once thawed, gradually increase the temperature of the running water to heat the milk to the appropriate feeding temperature.

Tip: I found it to be easiest to freeze breast milk in breast milk freezer bags. I froze 3-4 ounces at a time and laid each bag flat on its side while in the freezer. This allowed the frozen milk to thaw more quickly.

Warming refrigerated milk

  • Hold the refrigerated milk under warm running water for several minutes.
  • You can also immerse the storage container in a pot of previously heated water but do not heat refrigerated breast milk directly on the stove.

Tip: Some babies don't require that their refrigerated milk be warmed. Try giving the refrigerated milk to your baby to see if he or she will accept it.

Guidelines for thawed milk

Previously frozen breast milk that has been thawed can be stored in the refrigerator for up to 24 hours. At this point in time, the safest practice is to not refreeze thawed breast milk.

Important warming tips

  • Never bring the temperature of breast milk to a boiling point.
  • You may notice that the stored breast milk may separate into two layers -- this is perfectly normal. One layer is the milk layer, the other is the cream layer. Swirl the storage container or bottle gently to evenly redistribute the cream before feeding it to your baby.
  • Never microwave stored breast milk. Microwaving can cause a loss of the beneficial properties and leave hot spots, which are dangerous for your baby.

Lipase, milk fats and breastfeeding

If your thawed breast milk has a sour smell or soapy taste, you could have a high breakdown of milk fats. Don't worry though, your milk is still considered safe for your baby's consumption. The sour or rancid smell of thawed milk is caused by high lipase activity due to the milk being chilled or frozen. If your baby will not drink the (stinky) thawed milk, you can scald (not boil) your freshly expressed milk then quickly cool it before freezing it. This method deactivates the lipase enzyme and is considered completely safe for your baby.

Source: La Leche Leage International

More about breastfeeding

Breastfeeding support: Common breastfeeding problems and solutions
Safe practices for warming and sterilizing bottles
Safe practices for storing expressed breast milk


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