You pumped, got pulled away, and now there is a bottle on the counter. How long can breast milk sit out before it has to go? Here are the CDC’s room-temperature limits for fresh, thawed and leftover milk, in one simple chart.
Storing milk well is part of an easier breastfeeding routine. If you are still finding your rhythm, start with our breastfeeding latch guide.
For feeds, amounts and schedules by age, see our baby feeding topic page.
Quick answer: how long can breast milk sit out?
Freshly pumped breast milk can sit out at room temperature (77°F or colder) for up to 4 hours, according to the CDC. Thawed or warmed milk should be used within 2 hours. Milk left in the bottle after a feeding should be thrown away 2 hours after your baby finishes.
- Fresh milk, room 77°F (25°C) or colder: up to 4 hours
- Thawed or warmed milk: use within 2 hours, never refreeze
- Leftovers after a feed: discard 2 hours after your baby finishes
Breast milk storage times at a glance
| Type of milk | Room temperature (77°F or colder) | Refrigerator | Freezer |
|---|---|---|---|
| Freshly pumped | Up to 4 hours | Up to 4 days | About 6 months is best; up to 12 months is acceptable |
| Thawed | Use within 2 hours once at room temperature or warmed | Use within 24 hours after it is fully thawed | Never refreeze |
| Left over after a feed | Discard 2 hours after your baby finishes | Not listed | Not listed |
Source: CDC. The AAP gives the same room-temperature limit for freshly expressed milk (up to 4 hours) and advises chilling it as soon as possible.
Why the limits are different
The CDC uses one clock for fresh milk and a shorter one for milk that has been thawed, warmed or partly drunk. Room temperature matters too: the 4-hour limit is for rooms at 77°F (25°C) or colder. In a warmer room, the cautious choice is to chill the milk sooner.
What to do with milk that has been sitting out
- Check when it was pumped. The CDC advises labeling milk with the date it was expressed. Adding the time makes the 4-hour count easy.
- Under 4 hours in a room at 77°F or colder: use it, or move it to the fridge or freezer.
- Over 4 hours, a warm room, or not sure: the cautious choice is to throw it out.
- Thawed or warmed milk: use within 2 hours. Never refreeze thawed milk.
- A partly finished bottle: use within 2 hours after your baby finishes, then discard the rest.
- On the go: the CDC says an insulated cooler with frozen ice packs can hold milk for up to 24 hours. Then use it, refrigerate it or freeze it.
More travel ideas are in our guide to feeding your baby on the go.
Warming is optional: the CDC says breast milk can be served at room temperature or cold. If you warm it, use warm water, never the microwave. See our list of bottle feeding mistakes to avoid.
Mixing breast milk and formula feeds? Formula has its own, shorter rules. Our combination feeding guide helps you plan both.
Related: how long formula can sit out after mixing.
Related: a pumping schedule to increase supply.
When to talk to your doctor
- Your baby was born early, is in the hospital or has a medical condition: ask the care team which storage rules to follow
- Your baby has vomiting, diarrhea or a fever, or seems unwell after a feed
- Your baby is under 3 months and has a temperature of 100.4°F (38°C) or higher: call right away
- You have trouble pumping or storing enough milk: your pediatrician or a lactation consultant can help
Frequently asked questions
Does breast milk need to be warmed?
No. The CDC says breast milk does not need to be warmed and can be served at room temperature or cold. If you warm it, set the sealed container in warm water and test a few drops on your wrist.
How long does breast milk last in the fridge?
Freshly pumped milk keeps in the refrigerator for up to 4 days, according to the CDC. Store it at the back, not in the door, where the temperature changes each time the door opens.
Can I microwave breast milk?
No. The CDC says never to thaw or heat breast milk in a microwave, because it can create hot spots that can burn your baby’s mouth. The AAP gives the same warning.
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Sources
- CDC: Breast Milk Storage and Preparation
- HealthyChildren.org (AAP): Storing and Preparing Expressed Breast Milk
This article is for general information only and is not a substitute for medical advice. If you’re worried about your baby, call your pediatrician, or 911 in an emergency.