Breast Milk Storage: How Long It Lasts and How to Handle It

Pumping takes real effort, so you want every ounce to stay safe. Happily, breast milk storage comes down to a few simple rules: know the numbers, build a few good habits, and you can store, freeze and serve your milk with confidence.

The times below follow the current guidance from the Centers for Disease Control and Prevention (CDC) for healthy, full-term babies. If your baby was born early or is in the hospital, check with your baby’s care team, because hospitals often use stricter rules.

Breast milk storage guidelines at a glance

Type of milk	Where it’s kept	How long it’s good for
Freshly expressed	Room temperature, 77°F (25°C) or colder	Up to 4 hours
Freshly expressed	Insulated cooler with frozen ice packs	Up to 24 hours (then use, refrigerate or freeze)
Freshly expressed	Fridge, 40°F (4°C) or colder	Up to 4 days
Freshly expressed	Freezer, 0°F (-18°C) or colder	Within 6 months is best, up to 12 months is acceptable
Freshly expressed	Deep (chest or upright) freezer, -4°F (-20°C)	Same CDC limit: best within 6 months, up to 12 months
Thawed, previously frozen	Room temperature	1–2 hours
Thawed, previously frozen	Fridge	Up to 24 hours from when it is fully thawed
Thawed, previously frozen	Freezer	Never refreeze thawed milk
Leftover from a feed	Any	Use within 2 hours after your baby finishes, then discard

The CDC gives one freezer guideline for any freezer at 0°F (-18°C) or colder. The American Academy of Pediatrics (AAP) lists up to 9 months in a fridge-freezer and up to 12 months in a chest or deep freezer at -4°F (-20°C). Either way, using frozen milk within 6 months is best.

Not sure which rule applies to a particular bottle? Our breast milk storage calculator gives you a use-by time based on when you pumped and where the milk is stored.

How long breast milk lasts, place by place

A few details for each spot:

• Fridge: milk keeps up to 4 days, best at the back of the shelf. See how long breast milk lasts in the fridge for tips on fridge temperature and when to freeze instead.
• Counter: the 4-hour limit only applies in a room at 77°F (25°C) or cooler. Our guide on how long breast milk can sit out covers fresh, thawed and leftover milk.
• Freezer: freeze milk early if you won’t use it within 4 days, and use the oldest milk first.

Containers and labeling

• Use breast milk storage bags or clean, food-grade glass or plastic containers with tight-fitting lids.
• Don’t use disposable bottle liners or plastic bags that aren’t made for breast milk.
• Label every container with the date you expressed the milk. For daycare, add your baby’s name and check the provider’s own rules.
• Wash your hands before pumping or handling milk, and keep pump parts clean. Our pumping guides cover the equipment side.

Freezing tips: small, flat and at the back

• Store small amounts. Freeze 2 to 4 ounces (60 to 120 ml), or about one feed, so you thaw only what your baby needs.
• Leave room at the top. Milk expands as it freezes, so leave about 1 inch (2.5 cm) of space in a container.
• Freeze bags flat. Squeeze out the air, seal, and lay bags flat until frozen. Flat bags stack neatly and thaw faster.
• Skip the door. Store milk at the back of the fridge or freezer, where the temperature changes least when the door opens.
• Cool before combining. Chill freshly pumped milk before adding it to milk that is already cold or frozen.

Building a stash around work? Plan it with a realistic pumping schedule and use the oldest milk first.

Thawing and warming

Thaw milk in the fridge overnight, in a bowl of lukewarm water, or under lukewarm running water. Never thaw or heat breast milk in a microwave, which heats unevenly and can scald your baby. Step-by-step guides:

• How to thaw frozen breast milk, including why you shouldn’t refreeze it
• How to warm breast milk, and how long warmed milk stays good

Warming is optional: many babies drink breast milk cold or at room temperature.

Combining breast milk with formula, and other questions

If you combination feed, you can put breast milk and formula in the same bottle as long as the formula is mixed with water first. Read our guide to mixing breast milk and formula for the safe order and timing.

You may also have seen freeze-dried milk powder online. Before trying it, read our honest look at turning breast milk into powder at home and why freezing is still the method health agencies back.

When to ask for help

Talk to your baby’s doctor if your baby seems unwell after a feed, or if you’re unsure whether milk is still safe. If in doubt, throw it out. For pumping and storage questions, an International Board Certified Lactation Consultant (IBCLC) or a La Leche League leader can help; see our list of breastfeeding support options.