How can breastmilk be thawed?

Expressed milk can be thawed in the refrigerator, in a container of (warm) water, or under running (warm) water. Milk does not need to be warmed. It can be served at room temperature or cold. If you decide to warm the breastmilk, keep the container sealed and place the sealed container into a bowl of warm, not hot, water or hold it under warm running water for a few minutes. Test the milk’s temperature before feeding it to your baby by putting a few drops on your wrist.1 2 3

Please note that it is not advisable to defrost breastmilk in the microwave. Microwave ovens do not heat liquids evenly which could easily scald a baby or damage the milk and bottles may explode if left in the microwave too long. Microwave heating can also cause a significant decrease in the activity of anti-infective properties. Microwaving appears to be contraindicated at high temperatures and there are questions with regard to its safety even at low temperatures.4

Thawed milk is safe at room temperature (up to 25ºC/77ºF) for 1 to 2 hours and up to 24 hours in the fridge.

In general, when food has thawed in the refrigerator, it is safe to refreeze it without cooking.5 There is however little information on refreezing thawed human milk. Bacterial growth and loss of antibacterial activity in thawed milk will vary depending on the technique of milk thawing, duration of the thaw, and the number of bacteria in the milk at the time of expression.6 Please see How can breastmilk be reused for further information.

Next: How can breastmilk be pasteurized at home?

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  1. Please note: Some parents have experienced leakage with their storage bags when thawing them. Thawing storage bags of breastmilk is best done by handling them with clean hands, wiping the outside of the bag clean, and putting them in a bowl to collect any potentially leaked breastmilk. ↩︎
  2. OASH – Pumping and storing breastmilk ↩︎
  3. CDC – Proper Storage and Preparation of Breast Milk ↩︎
  4. Richard Quan, et al. 1992. Effects of Microwave Radiation on Anti-infective Factors in Human Milk ↩︎
  5. USDA – Freezing and Food Safety ↩︎
  6. Anne Eglash, et al. BREASTFEEDING MEDICINE Volume 12, Number 7, 2017. ABM Clinical Protocol #8: Human Milk Storage Information for Home Use for Full-Term Infants ↩︎