Breast Milk Storage Guidelines: Fridge, Freezer, Counter

Freshly pumped breast milk keeps up to 4 hours at room temperature, up to 4 days in the fridge and about 6 months in the freezer, with up to 12 months acceptable. These are the breast milk storage guidelines of the CDC, also used by the Office on Women's Health. The chart below covers every situation, including thawed, warmed and leftover milk, the ones parents ask about most.

Breast milk storage chart

Situation	How long	Good to know
Freshly pumped, room temperature (77°F or colder)	Up to 4 hours	Covered, kept as cool as possible
Fridge (40°F or colder)	Up to 4 days	In the back, never in the door
Freezer (0°F or colder)	About 6 months is best, up to 12 months is acceptable	In the back, never in the door
Insulated cooler with frozen ice packs	Up to 24 hours	Then use it, refrigerate it or freeze it
Thawed, in the fridge	Up to 24 hours	Counted from when it's completely thawed; never refrozen
Thawed, at room temperature	1 to 2 hours
Warmed or brought to room temperature	Within 2 hours
Left over from a feeding	Within 2 hours after your baby finishes	Then throw it out

Sources: the CDC's storage page and printable chart (October 2024), and the Office on Women's Health. Links are at the end of the article. These guidelines are written for healthy, full-term babies: if your baby was born prematurely or is in the hospital, the hospital team may have its own rules.

How long can breast milk sit out at room temperature?

Up to 4 hours, at 77°F or colder, according to the CDC. The Office on Women's Health suggests keeping the container covered and as cool as possible, for example under a clean, cool towel. If you won't use the milk within a few hours, put it in the fridge: the CDC notes that breast milk doesn't spoil as quickly at cooler temperatures.

Some pages give longer times. The AAP's HealthyChildren.org mentions 6 to 8 hours if the milk was expressed very cleanly, while adding that it's best to chill it as soon as possible, and the Academy of Breastfeeding Medicine says the same. The CDC's 4 hours is the simpler rule to follow.

How long does breast milk last in the fridge?

Up to 4 days, in a fridge at 40°F or colder. Three tips come up in the official sources:

in the back, never in the door: the CDC explains that the back of the fridge is protected from temperature changes when the door opens and closes;
an appliance thermometer if your fridge doesn't show its temperature (CDC);
freeze right away any milk you don't think you'll use within 4 days, to protect its quality (CDC).

After 4 days in the fridge, the CDC says to use the milk or throw it away.

Can you add freshly pumped milk to milk already in the fridge?

Yes, once it has cooled. The CDC advises against adding warm, freshly pumped milk to milk that's already cold or frozen, because it rewarms the older milk: chill the new milk first, then combine them. The storage time is then based on the oldest milk in the container.

How long does breast milk last in the freezer?

At 0°F or colder, about 6 months is best, and up to 12 months is acceptable (CDC). Freezing keeps milk safe for a long time, but its quality slowly declines, which is why these times still matter. The type of freezer doesn't matter as long as it stays at 0°F or colder, the CDC adds; deep freezers and chest freezers can be colder.

The AAP's HealthyChildren.org splits it differently: up to 9 months in a freezer with its own door at 0°F, and up to 12 months in a chest or deep freezer at -4°F.

To freeze milk:

2 to 4 oz per bag, or the amount offered at one feeding, so you only thaw what your baby will drink (CDC);
leave about one inch at the top, because milk expands as it freezes;
in the back of the freezer, not on the door shelves;
count the milk's age from the first time it was frozen, even if you move it to another freezer later (CDC).

How long is thawed breast milk good for?

24 hours in the fridge, counted from when the milk is completely thawed, not from when you took it out of the freezer (CDC). At room temperature, thawed milk is used within 1 to 2 hours. And thawed milk is never refrozen.

The one exception the CDC mentions: milk that has started to thaw but still contains ice crystals, for example during a power outage, can be refrozen.

To thaw, always start with the oldest milk ("first in, first out"), then:

in the fridge overnight;
in a bowl of warm or lukewarm water;
under lukewarm running water.

Never in the microwave: the CDC explains that microwaving can destroy nutrients in breast milk and create hot spots, which can burn a baby's mouth.

How do you warm breast milk, and how long does it last once warmed?

Breast milk doesn't need to be warmed: it can be served cold or at room temperature (CDC). To warm it, keep the container sealed and set it in a bowl of warm water, or hold it under warm, but not hot, running water for a few minutes. Swirl it to mix the fat, which may have separated, then test a few drops on your wrist. Never heat it on the stove or in the microwave.

Once warmed or brought to room temperature, milk is used within 2 hours. A bottle your baby didn't finish is used within 2 hours after the feeding, then thrown out (CDC). Some AAP pages are stricter on leftovers and say to throw them out after 1 hour: if your pediatrician gives you a rule, follow it.

Bags, bottles and labels

Containers: breast milk storage bags, or clean, food-grade glass or plastic containers with tight-fitting lids. The CDC says never to use disposable bottle liners or plastic bags that aren't meant for breast milk. The Office on Women's Health recommends BPA-free plastic and avoiding containers with the recycle number 7.
Labels: the date the milk was pumped on every container, plus your baby's name if it goes to daycare (CDC).
Pump parts: cleaned after each use. The CDC suggests sanitizing them at least once a day, especially if your baby is under 2 months old, was born prematurely or has a weakened immune system.

With several bags in the fridge and the freezer, knowing which one to use first quickly becomes a puzzle, especially when two of you are feeding the baby. In Caasi, each pumping session becomes a numbered batch: you write the number on the bag, and the app tracks each batch's use-by time in the fridge or freezer, recalculates it when the batch is thawed, and both parents see the same milk stash. Getting ready to go back to work? See how much breast milk to store before going back.

Why do some sites give different storage times?

Because they follow different guidelines. The CDC adapted its chart from a protocol of the Academy of Breastfeeding Medicine, which allows longer times under very clean conditions: 6 to 8 hours at room temperature and 5 to 8 days in the fridge. The AAP's family pages give 9 months in a standard freezer at 0°F. Guidelines from other countries can be stricter.

This article follows the CDC. For your own situation, your pediatrician or a lactation consultant can help.

Frequently asked questions

Can you refreeze breast milk that has thawed?

No. The CDC says never to refreeze breast milk after it has thawed. The only exception is milk that still contains ice crystals, for example after a power outage: it can go back in the freezer.

Can breast milk go in a shared fridge at work?

Yes. The CDC says expressed breast milk is food: it can be stored alongside other food in any refrigerator meant for food, and coworkers shouldn't treat it as a biohazard. Label it with your name and the date you pumped it.

Pumped milk separated in the fridge: is it still good?

Yes. It's normal for the fat to rise and separate. The CDC suggests swirling the milk to mix it back in.

Can you bring pumped breast milk on a plane?

Yes. The CDC says that in the United States, breast milk is exempt from TSA limits on liquids: you can carry more than 3.4 ounces in your carry-on bag, along with ice and gel packs, even if you're not traveling with your baby.

Sources

The guidance in this article comes from the official sources listed above. It doesn't replace advice from your pediatrician, your doctor or a lactation consultant.