Breast milk storage guidelines
By The Zomee Team · Updated September 25, 2026 · 4 min read
According to the CDC, freshly pumped breast milk keeps up to 4 hours at room temperature and up to 4 days in the refrigerator. In the freezer, it's best within 6 months, and up to 12 months is acceptable.
These times are for healthy, full-term babies. The CDC notes they may vary for premature or sick babies, so if your baby's care team gave you different times, follow theirs.
How long can breast milk sit out?
Up to 4 hours in a room at 77°F or colder, according to the CDC. The room's temperature is especially important if you live in a warm climate or keep your home warm. If you won't use the milk within a few hours, refrigerate it.
If your baby doesn't finish a bottle, use the rest within 2 hours after the feed, the CDC says. After that, throw it out.
How long does breast milk last in a cooler?
Up to 24 hours in an insulated cooler with frozen ice packs, according to the CDC. When you arrive, use the milk right away, refrigerate it, or freeze it.
For travel or daycare, our Packable Breast Milk Cooler and Storage Bottles includes a cooler bag, two ice packs, and four storage bottles with caps.
How long does breast milk last in the refrigerator?
Up to 4 days at 40°F or colder, according to the CDC. Store it toward the back, not in the door. Milk further inside is better protected from temperature changes as the door opens and closes.
If you don't think you'll use it within 4 days, the CDC says to freeze it right away. Once milk has been refrigerated for 4 days, use it or throw it out.
How long does frozen breast milk last?
Within 6 months is best and up to 12 months is acceptable, in any freezer that stays at 0°F or colder, the CDC says. Keep milk out of the freezer door too.
Freeze your milk in storage bags made for breast milk, or in clean, food-grade glass or plastic containers with tight-fitting lids. The CDC suggests 2 to 4 oz per container, or the amount you offer at one feeding. Leave about an inch of space at the top, because milk expands as it freezes.
Label every container with the date you pumped it, and add your baby's name if the milk goes to childcare. Our Zomee Milk Storage Bags have measurement markings and space to write a name, the date, and the time.
How do I thaw frozen breast milk?
The CDC lists three ways: in the refrigerator overnight, in a bowl of warm or lukewarm water, or under lukewarm running water. Thaw your oldest milk first. Never thaw or heat breast milk in the microwave.
According to the CDC, thawed milk keeps up to 24 hours in the refrigerator. Start counting when it's completely thawed, not when you took it out of the freezer. At room temperature, thawed milk keeps 1 to 2 hours. Never refreeze milk after it has thawed.
The CDC storage chart
Storage times vary from source to source. The CDC says that's because temperature, temperature changes, and cleanliness while you pump and handle milk all affect how long it keeps. Wash your hands with soap and water before you pump or handle milk.
| Milk | Room temperature (77°F or colder) | Refrigerator (40°F) | Freezer (0°F or colder) |
|---|---|---|---|
| Freshly pumped | Up to 4 hours | Up to 4 days | Best within 6 months, up to 12 months acceptable |
| Thawed from frozen | 1–2 hours | Up to 24 hours from fully thawed | Never refreeze |
| Leftover from a feed | Use within 2 hours after the feed | Use within 2 hours after the feed | Use within 2 hours after the feed |
Where to get help
Call The Mom Line™ at 1-888-662-7159 for pump, sizing, parts, and support questions. Real moms and certified lactation consultants answer it.
For feeding or supply concerns, talk to a lactation consultant (IBCLC). For questions about your baby's health, call your baby's provider.
Questions moms ask
Can I add freshly pumped milk to milk that's already in the fridge or freezer?
Yes, once the fresh milk is cold. The CDC says warm milk can rewarm the older milk. Count the batch's storage time from the older milk's date.
Can I put a bottle my baby didn't finish back in the fridge?
You can, but refrigerating it doesn't give you more time. The CDC's chart gives leftover milk the same 2 hours after the feed in the refrigerator as on the counter.
How long is frozen breast milk safe if the power goes out?
About 48 hours in a full freezer and about 24 hours in a half-full one, if you keep the door closed, the CDC says. Once the power is back, milk that still has ice crystals can be refrozen. Put milk that has fully thawed but still feels cold in the refrigerator, and use it within a day or throw it out.
Do I need to warm breast milk before feeding it?
No. The CDC says breast milk can be served cold or at room temperature. To warm it, set the sealed container in a bowl of warm water, test a few drops on your wrist, and use the milk within 2 hours.
Why does my stored breast milk look separated?
The fat in breast milk may separate, the CDC says. Swirl the milk to mix it back in.
