How Long Is Breast Milk Good For? Storage, Refrigeration & Freezing Guide

Written & Medically Reviewed by Dr. G
Board-Certified Pediatrician · About Dr. G

Few things feel worse than looking at a bottle of pumped breast milk and wondering whether you have to throw it away.

You worked to produce it. You pumped it. You stored it.

Now you are asking: “How long is breast milk good for?”

Fortunately, the basic storage rules become much easier once you separate fresh, refrigerated, frozen, thawed, and leftover milk.

Breast Milk Storage Guidelines at a Glance

Fresh milk at room temperature	Up to 4 hours at 77°F (25°C) or cooler
Fresh milk in refrigerator	Up to 4 days at 40°F (4°C)
Fresh milk in freezer	6 months is best; up to 12 months is acceptable at 0°F (-18°C) or colder
Previously frozen milk, thawed in refrigerator	Use within 24 hours after it is completely thawed
Thawed milk warmed or brought to room temperature	Use within 2 hours
Milk left after a feeding	Use within 2 hours after feeding ends, then discard

These CDC guidelines are intended for healthy full-term infants. Hospitalized, premature, or medically fragile babies may need stricter guidance.

How Long Can Breast Milk Sit Out?

Freshly expressed breast milk can generally remain at room temperature of 77°F (25°C) or cooler for up to 4 hours.

That does not mean 4 hours is always the goal.

If you know the milk will not be used soon, refrigerate it promptly. Milk kept in a cooler room remains safer longer than milk exposed to a warm environment.

If the room is unusually warm or you are unsure how warm the milk became, use a more cautious approach.

How Long Is Breast Milk Good in the Refrigerator?

Freshly expressed breast milk can generally be refrigerated for up to 4 days at 40°F (4°C).

If you do not expect to use the milk within several days, CDC recommends freezing it as soon as possible rather than waiting until the fourth day.

Where Should I Store Breast Milk in the Refrigerator?

Store breast milk toward the back of the refrigerator, where the temperature remains more consistent.

Avoid storing it in the refrigerator door because the temperature changes more each time the door opens.

How Long Is Frozen Breast Milk Good For?

At 0°F (-18°C) or colder, CDC recommends using frozen breast milk within about 6 months for best quality.

Storage for up to 12 months is considered acceptable.

Label every container with the date the milk was expressed and generally use the oldest milk first.

How Should I Freeze Breast Milk?

How Much Breast Milk Should I Freeze in Each Bag?

Small portions are usually easier to manage.

AAP parent guidance suggests freezing approximately 2 to 4 ounces at a time to help reduce waste.

You can always thaw more if your baby is still hungry.

How Do I Thaw Frozen Breast Milk?

Safe options include:

• thawing overnight in the refrigerator,
• holding the sealed container under lukewarm running water, or
• placing the sealed container in a bowl of warm or lukewarm water.

Do not use boiling water.

And never microwave breast milk.

Why Shouldn't I Microwave Breast Milk?

Microwaving can heat milk unevenly and create hot spots that can burn your baby's mouth.

CDC also notes that microwaving can damage some of the milk's nutritional components.

Breast milk does not need to be warmed at all if your baby accepts it cold or at room temperature.

How Long Is Thawed Breast Milk Good For?

Once frozen milk has completely thawed in the refrigerator, CDC recommends using it within 24 hours.

Start counting those 24 hours when the milk is completely thawed—not when you first move the frozen container into the refrigerator.

Once thawed milk has been brought to room temperature or warmed, use it within 2 hours.

Can I Refreeze Thawed Breast Milk?

Do not refreeze breast milk after it has completely thawed.

There is an important exception during a freezer failure or power outage: if the milk has started to thaw but still contains ice crystals, CDC says it can be refrozen.

How Long Is Breast Milk Good After My Baby Drinks From the Bottle?

Once your baby begins drinking, bacteria from the baby's mouth can enter the milk.

CDC recommends using the remaining milk within 2 hours after your baby finishes feeding.

After that, discard what remains.

Can I Mix Fresh Breast Milk With Refrigerated Breast Milk?

Yes, but CDC advises cooling the newly expressed milk before adding it to milk that is already cold.

Adding warm milk directly to older refrigerated or frozen milk can rewarm the older milk.

When combining milk pumped at different times, base the storage time on the oldest milk in the container.

Can I Combine Milk From Different Pumping Sessions?

Yes.

Cool the newer milk first, then combine it with milk that is already refrigerated.

Date the combined container based on the oldest milk.

Does Breast Milk Have to Be Warmed?

No.

Breast milk can be served cold, at room temperature, or gently warmed.

Warming is mostly a matter of your baby's preference.

Why Does Refrigerated Breast Milk Separate?

Separation is normal.

The fat may rise to the top while a thinner layer remains underneath.

Gently swirl the container to mix the layers before feeding.

Separation does not mean the milk has spoiled.

Why Does My Stored Breast Milk Smell Different?

Stored human milk can sometimes smell or taste different from freshly expressed milk.

A change in smell by itself does not automatically mean the milk is unsafe.

However, milk that has exceeded recommended storage times, was stored too warm, or is clearly spoiled should be discarded.

What Container Should I Use for Breast Milk?

CDC recommends:

• breast milk storage bags, or
• clean food-grade glass or plastic containers with tight-fitting lids.

Do not use ordinary household plastic bags or disposable bottle liners that were not designed for breast milk storage.

Do Breast Milk Containers Need to Be Sterilized?

For healthy full-term babies, clean containers and careful handling are generally appropriate.

Premature babies, infants younger than 2 months, or babies with weakened immune systems may need additional sanitation precautions for feeding equipment.

Follow your baby's healthcare team's guidance if your baby is medically vulnerable.

How Long Can Breast Milk Stay in a Cooler?

CDC says breast milk can be stored and transported in an insulated cooler with frozen ice packs for up to 24 hours.

At your destination, use the milk, refrigerate it, or freeze it as appropriate.

What If the Power Goes Out?

Keep refrigerator and freezer doors closed as much as possible.

CDC says:

• An unopened refrigerator generally keeps food cold for about 4 hours.
• A full freezer can stay cold for about 48 hours.
• A half-full freezer may stay cold for about 24 hours.

Once power returns:

• If frozen milk still contains ice crystals, it can be refrozen.
• If it is completely thawed but still cold, refrigerate it and use it within the next day.
• If you cannot determine that the milk stayed safely cold, discard it.

What If I Don't Know How Long Breast Milk Has Been Out?

If the storage history is genuinely unknown, it is safer to discard the milk rather than guess.

Labeling milk immediately after pumping prevents many of these situations.

When Should I Call My Pediatrician?

When Is Illness More Urgent?

Frequently Asked Questions

References