How to thaw breast milk
Thaw frozen breast milk in the refrigerator overnight, in a bowl of warm or lukewarm water, or under lukewarm running water. Never use a microwave. Use milk thawed in the fridge within 24 hours, and never refreeze it.
How to thaw frozen breast milk
The CDC lists three safe ways to thaw breast milk:
- In the refrigerator overnight.
- In a bowl of warm or lukewarm water. Put the sealed bag or bottle in the water until the milk thaws.
- Under lukewarm running water. Hold the sealed container under the tap.
Never thaw or heat breast milk in a microwave.
First in, first out: the CDC says to always thaw the oldest milk first. Labeling each container with the date it was pumped makes that easy.
How long does thawed breast milk last?
How long you have depends on where the thawed milk is:
| Thawed milk | Use it within |
|---|---|
| Thawed in the refrigerator | 24 hours |
| Brought to room temperature or warmed | 2 hours |
| Left over after a feeding | 2 hours, then discard |
Can you refreeze thawed breast milk?
No. The CDC says never to refreeze breast milk after it has thawed. If you won’t use thawed milk within its time, discard it. Storing small amounts, 2 to 4 ounces or one feeding’s worth, helps avoid waste (CDC).
How to warm breast milk
Breast milk does not need to be warmed: the CDC notes it can be served at room temperature or cold. If your baby prefers it warm:
- Put the sealed container in a bowl of warm water, or hold it under warm, not hot, running water.
- Don’t heat breast milk directly on the stove or in the microwave.
- Swirl the milk to mix the fat, which may have separated.
- Before feeding, test the temperature by putting a few drops on your wrist.
Once milk has been warmed, use it within 2 hours.
Leftovers
If your baby doesn’t finish the bottle, use the leftover milk within 2 hours. After that, discard it. Don’t save it for another day.
Why does thawed milk smell different?
Refrigerated and frozen milk can smell different from fresh milk. The Academy of Breastfeeding Medicine (ABM) explains that this comes from lipase, an enzyme in milk that breaks down fat. This process also has antimicrobial effects. ABM found no evidence that babies often reject milk because of this smell.
If the smell is soapy or metallic and your baby refuses the milk, read about high lipase milk. Milk that smells distinctly sour or rancid is a different matter: don’t use it.
How long can frozen milk stay frozen?
In a freezer, about 6 months is best, and up to 12 months is acceptable (CDC). The full table, with a checker for your own bags, is on how long breast milk lasts.
Know when every thawed bag runs out
In Milkly, mark a bag as thawed and it gets its own deadline, 24 hours by default, following the CDC. Bags near the end of their storage window are shown, so the oldest milk goes first.
Tracking by bag is part of Pro, and your first week is on Pro.
Related: how long breast milk lasts · high lipase milk · how much milk a baby needs.
Sources
- CDC, Breast Milk Storage and Preparation (updated 2026-08-14)
- Academy of Breastfeeding Medicine, Clinical Protocol #8: Human Milk Storage Information for Home Use for Full-Term Infants, revised 2017
Last reviewed:
This page summarizes CDC guidance and the Academy of Breastfeeding Medicine protocol for healthy, full-term babies. It is not medical advice. If your baby was born early or is in hospital, follow your baby's care team.