Milk & formula storage · Breast milk storage
Breast milk storage guidelines: room temperature, fridge and freezer
Last reviewed November 2026 against AAP, CDC, NHS and WHO guidance · Sources
Quick answer
Freshly expressed breast milk keeps up to 4 hours at room temperature (77°F or cooler), up to 4 days in the fridge, and about 6 months in the freezer, with up to 12 months acceptable, according to the CDC. Use thawed milk within 24 hours and leftovers within 2 hours.
- Room temp
- 4 hours
- Fridge
- 4 days
- Freezer
- 6–12 months
On this page
How long does breast milk last?
This chart covers every situation the CDC lists. Tap through to the page for each one for the details that trip parents up.
| Where | Freshly expressed | Thawed from frozen |
|---|---|---|
| Room temperature, 77°F (25°C) or cooler | Up to 4 hours | Use within 2 hours once at room temperature or warmed |
| Fridge, 40°F (4°C) | Up to 4 days | Use within 24 hours of fully thawing |
| Freezer, 0°F (-18°C) | About 6 months is best; up to 12 months is acceptable | Never refreeze |
| Insulated cooler bag with frozen ice packs | Up to 24 hours while traveling | Not covered by CDC; use it, chill it or freeze it on arrival |
| Leftover after a feed | Use within 2 hours after your baby finishes | Use within 2 hours after your baby finishes |
What should I store breast milk in?
The CDC recommends clean glass or plastic containers with tight lids, or bags made for storing breast milk. Never use disposable bottle liners or plastic bags that aren't meant for breast milk.
Freeze in 2 to 4 oz (60 to 120 ml) portions, or the amount your baby takes at one feed, so you don't thaw more than you need. Leave about an inch of space at the top, because milk expands as it freezes.
Where in the fridge or freezer should milk go?
At the back of a shelf, not in the door. The CDC says not to store breast milk in the door of the fridge or freezer, where the temperature swings every time it opens.
If you won't use fresh milk within 4 days, freeze it right away rather than letting it sit in the fridge first.
Does breast milk need to be warmed?
No. The CDC says breast milk can be served cold or at room temperature. If your baby prefers it warm, stand the container in a bowl of warm water or hold it under warm (not hot) running water, then test a few drops on your wrist.
Never heat breast milk in a microwave or directly on the stove. Swirl the milk to mix back in any fat that has separated.
How do I keep track of the clock at 3am?
Storage rules all start from a time: when you pumped, when it thawed, when you mixed it, when the feed began. Those are exactly the times tired parents forget, especially when someone else made the bottle.
- Label every container of expressed milk with the date (and time, if you'll use it within days).
- Write the mixing time on a formula bottle you've put in the fridge, or tape a note to the fridge.
- Note when each feed starts. That's the clock for the 1-hour formula rule and the 2-hour leftover milk rule.
Feedoo Baby logs the time of every feed and who gave it, so whoever takes the next shift can see when the last bottle started. See how to track baby feeding for a simple routine.
When to call your pediatrician
- A rectal temperature of 100.4°F (38°C) or higher in a baby 3 months or younger. The AAP says to call right away, even if your baby seems otherwise well.
- Fewer wet diapers than expected for their age (fewer than 6 a day from about day 5), or dark yellow urine.
- Very sleepy and hard to wake for feeds, floppy, or unusually quiet.
- Refusing feeds, or feeding poorly several times in a row.
- Signs of dehydration: dry mouth, no tears, or a sunken soft spot on the head.
- Forceful or green vomiting, or vomiting after most feeds.
- Red, black (after the first meconium poops) or white/pale gray poop.
- Yellow skin or eyes that spread or deepen, or any yellow color in the first 24 hours.
- Trouble breathing, blue or gray lips, or your baby is limp or very hard to wake: call 911 (or your local emergency number) now.
If something feels wrong, trust that feeling and call. You never need a reason beyond worry.
Questions parents ask
How long is breast milk good for after pumping?
Up to 4 hours at room temperature (77°F or cooler), up to 4 days in the fridge, or about 6 months in the freezer, with up to 12 months acceptable, according to the CDC.
Can I mix fresh breast milk with milk that's already chilled?
The CDC's storage page focuses on time limits rather than combining batches. A common approach is to chill fresh milk first, then add it to cold milk, and date the container by the oldest milk in it. Ask your lactation consultant if you're unsure.
Which frozen milk should I use first?
The oldest. The CDC suggests thawing the oldest milk first, which is why labeling each container with the date matters.
Is it normal for stored breast milk to separate?
Yes. The fat rises to the top. Swirl the container gently to mix it back in before feeding.
Related guides
- How long can breast milk sit out at room temperature?Freshly pumped breast milk can sit out up to 4 hours at 77°F or cooler. Thawed or warmed milk gets 2 hours. What changes in a hot room, plus CDC sources.
- How long is breast milk good in the fridge?Fresh breast milk lasts up to 4 days in the fridge at 40°F. Thawed milk gets 24 hours. Where to put it, when to freeze it instead, and the CDC rules.
- How long can you freeze breast milk?Frozen breast milk is best used within about 6 months and is acceptable up to 12 months, per the CDC. Portion sizes, containers and safe thawing.
- How long is formula good for?Mixed formula: use within 2 hours, 1 hour once feeding starts, 24 hours in the fridge. Opened powder: most within 1 month. Every CDC formula rule in one place.
- How to track baby feeding and diapersWhy pediatricians ask about feeds and diapers, exactly what to log for breast, bottle and combo feeding, and paper vs notes app vs tracking app compared.
Free tools
Sources
Last reviewed November 2026. Numbers are ranges from these public health sources; 1 oz ≈ 30 ml.
Feedoo Baby shares general information, not medical advice. Every baby is different. If you're worried about feeding, weight gain, diapers or your baby's health, call your pediatrician, midwife or health visitor.