How long can breast milk sit out at room temperature?

Freshly expressed breast milk can sit at room temperature (up to 77°F / 25°C) for up to 4 hours. Previously frozen and thawed milk should be used within 1-2 hours at room temperature.

How long does breast milk last in the fridge?

Fresh breast milk lasts up to 4 days in the refrigerator (40°F / 4°C or below), with 3 days being optimal for quality. Store it in the back of the fridge, not in the door. Thawed milk should be used within 24 hours.

Can you refreeze thawed breast milk?

No. Once breast milk has been thawed, it should never be refrozen. Thawed milk must be used within 24 hours if stored in the refrigerator, or within 1-2 hours at room temperature.

Breast Milk Storage Guide

How long can breast milk sit out? How long does it last in the fridge or freezer? Quick reference based on CDC and AAP guidelines.

Countertop / Room Temperature

Up to 77°F (25°C)

Fresh Milk

Up to 4 hours

Thawed Milk

1-2 hours

Tips

Cover the container and keep away from direct sunlight and heat
If the room is very warm (above 77°F), use within 1 hour
Discard any milk left out for more than 4 hours
Milk left over from a feeding should be used within 2 hours

Insulated Cooler with Ice Packs

5-39°F (−15 to 4°C)

Fresh Milk

Up to 24 hours

Thawed Milk

Do not re-store

Tips

Keep ice packs in contact with milk containers at all times
Limit how often you open the cooler
Transfer to refrigerator or freezer as soon as possible
Good option for commuting or traveling

Refrigerator

40°F (4°C) or below

Fresh Milk

Up to 4 days (optimal: 3 days)

Thawed Milk

Up to 24 hours

Tips

Store in the back of the refrigerator, not in the door
Use within 3 days for best quality
If you won't use it within 4 days, freeze it
Previously frozen then thawed milk must be used within 24 hours

Freezer (standard fridge-freezer)

0°F (−18°C) or below

Fresh Milk

Up to 6 months (optimal); up to 12 months (acceptable)

Thawed Milk

Never refreeze thawed milk

Tips

Store in the back of the freezer, away from the door
Use within 6 months for best quality
Leave 1 inch of space at the top of containers — milk expands when frozen
Label each container with the date it was pumped
Use the oldest milk first (first in, first out)

Deep Freezer

−4°F (−20°C) or below

Fresh Milk

Up to 12 months

Thawed Milk

Never refreeze

Tips

Best option for long-term storage
Quality is best within 6 months even in deep freezer
Consider using breast milk storage bags to save space

Quick Reference

Location	Temp	Fresh	Thawed
Countertop / Room Temperature	Up to 77°F (25°C)	Up to 4 hours	1-2 hours
Insulated Cooler with Ice Packs	5-39°F (−15 to 4°C)	Up to 24 hours	Do not re-store
Refrigerator	40°F (4°C) or below	Up to 4 days (optimal: 3 days)	Up to 24 hours
Freezer (standard fridge-freezer)	0°F (−18°C) or below	Up to 6 months (optimal); up to 12 months (acceptable)	Never refreeze thawed milk
Deep Freezer	−4°F (−20°C) or below	Up to 12 months	Never refreeze

How to Thaw Breast Milk

Thaw in the refrigerator overnight (safest method)
Place sealed container in warm (not hot) water to thaw more quickly
Never microwave breast milk — it creates hot spots and destroys nutrients
Gently swirl (don't shake vigorously) to mix the fat layer back in
Thawed milk may look different in color or consistency — this is normal
Use thawed milk within 24 hours and never refreeze
Thawed milk may smell or taste soapy due to lipase — this is safe

Storage Container Tips

Use BPA-free plastic bottles or glass containers with tight lids
Breast milk storage bags designed for freezing work well
Store in small amounts (2-4 oz) to reduce waste
Leave room at the top for expansion when freezing
Label with date, time, and amount pumped
Do not add warm milk to already frozen milk — cool it first

Never microwave breast milk. Never refreeze thawed breast milk. When in doubt, throw it out.

Sources