Quick answer: the “rule of 4s”
- Room temperature (77°F/25°C or colder): up to 4 hours
- Refrigerator (40°F/4°C): up to 4 days
- Freezer (0°F/-18°C): about 6 months is best, up to 12 months acceptable
- Thawed milk: use within 24 hours in the fridge, and never refreeze.
- Once warmed or brought to room temperature: use within 2 hours.
Breast milk storage chart
| Type of milk | Countertop (77°F or colder) | Refrigerator (40°F) | Freezer (0°F or colder) |
|---|---|---|---|
| Freshly pumped | Up to 4 hours | Up to 4 days | About 6 months best; up to 12 months |
| Thawed, previously frozen | 1–2 hours | Up to 24 hours | Never refreeze |
| Leftover from a feeding | Use within 2 hours after your baby finishes, then throw away | ||
These times are for healthy, full-term babies. If your baby is in the hospital or was born early, follow your care team’s instructions.
Storage tips
- Use clean, food-grade containers or breast milk storage bags with tight lids. Avoid regular plastic bags.
- Label every container with the date you pumped it.
- Store milk in small portions of 2–4 oz to cut waste.
- Leave space at the top of containers, since milk expands as it freezes.
- Keep milk at the back of the fridge or freezer, not in the door.
- Use the oldest milk first.
- Freshly pumped milk can be carried in an insulated cooler with ice packs for up to 24 hours.
How to thaw breast milk
- Overnight in the fridge (best), then use within 24 hours.
- Under lukewarm running water or in a bowl of warm water.
- Never thaw or heat milk in the microwave; it creates hot spots and can damage nutrients.
How to warm breast milk
Babies can drink milk cold, at room temperature or warmed. To warm it, place the sealed container in warm water or use a bottle warmer, swirl to mix the fat back in, and test on your wrist.
Combining milk from different sessions
Cool freshly pumped milk in the fridge before adding it to milk that’s already chilled, and use the date of the oldest milk on the label. Don’t add warm milk to frozen milk.
Why does my thawed milk smell soapy?
Some people have milk with a lot of lipase, an enzyme that breaks down fat, which can give thawed milk a soapy or metallic smell. It’s generally safe, but some babies refuse it. Ask a lactation consultant about scalding milk before freezing if this happens to you.
Need longer storage?
If your freezer is overflowing or you’re traveling, freeze-drying breast milk turns frozen milk into a shelf-stable powder.
Frequently asked questions
How long can breast milk sit out?
Freshly pumped breast milk can stay at room temperature (77°F or colder) for up to 4 hours.
How long is breast milk good in the fridge?
Up to 4 days at 40°F, stored at the back of the fridge.
How long does frozen breast milk last?
About 6 months is best, and up to 12 months is acceptable in a freezer at 0°F or colder.
Can you refreeze thawed breast milk?
No. Once breast milk has thawed, use it within 24 hours and never refreeze it.
Can I reuse breast milk my baby didn’t finish?
Use leftover milk within 2 hours after the feeding ends, then throw it away.
