Can I store pumped breast milk in a bottle?

Yes, it is safe to store pumped breast milk in bottles for later use. Properly storing breast milk helps preserve its nutritional and immunological properties so baby continues to benefit from your milk even when you are apart.

Quick Answers

– Pumped milk can be stored in milk storage bags, bottles, or other clean containers made for milk storage.

– Store milk in 2-4 oz portions to avoid waste since milk should not be reused once baby drinks from a bottle.

– Refrigerate milk immediately after pumping, and use within 3-5 days. Freeze for longer storage up to 6 months.

– Use milk storage bags, glass, or BPA-free plastic bottles. Do not use disposable bottle liners or regular plastic bags.

– Label milk with the date pumped before storing. Use oldest milk first.

– Thaw frozen milk overnight in the refrigerator or under warm running water. Do not microwave or boil.

– Once warmed, use milk within 1-2 hours. Do not refreeze or re-refrigerate thawed milk.

Storing Freshly Pumped Breast Milk

After you pump and collect milk, you’ll want to store it as quickly as possible to preserve its quality. Here are some tips for proper storage:

  • Refrigerate the milk right after pumping. Fresh milk can be kept at room temperature (up to 25°C or 77°F) for up to 4 hours, but it’s best to get it chilled as soon as possible.
  • Store milk in clean containers meant for breast milk. Opt for BPA-free bottles, milk storage bags, or glass bottles with tight-fitting lids.
  • Do not use regular plastic bags or disposable bottle liners, which are too thin and prone to leaking or bursting.
  • Divide milk into smaller 2-4 oz portions. Storing in small quantities helps prevent waste since unused milk from a bottle must be discarded once baby drinks from it.
  • Label each container with the date pumped before refrigerating. This helps you use the oldest milk first.

Once properly stored, refrigerated milk lasts for:

  • Up to 5 days if pumped for a full-term healthy baby
  • Up to 3 days if pumped for a preemie (less than 37 weeks)

The refrigerator temperature should remain steady at 39°F or colder. Keep milk towards the back where it is coldest. The freezer compartment inside a refrigerator is not ideal for longer freezing.

Thawing Refrigerated Milk

Thawing depends on how you intend to use the milk:

  • If giving milk cold, thaw overnight in the refrigerator. Gently swirl the bottle to mix any separated cream back in.
  • To warm milk, hold the sealed bottle under warm running water, and gently roll bottle to evenly distribute warmth. Do not overheat.
  • You can also run the sealed bottle under warm water until thawed, then place it in a container of warm water to heat. Change water every 15 minutes until desired temp.
  • Do not microwave breast milk due to the risk of dangerous hot spots that could burn baby’s mouth.

Once thawed and warmed, use the milk within 1-2 hours. Do not refreeze or return any leftover milk to the refrigerator.

Freezing Breast Milk for Later

Freezing is the optimal long-term storage method. Frozen milk retains its nutrient content and antibodies much better than refrigerated milk over time. Follow these guidelines for freezing milk:

  • Chill freshly pumped milk in the refrigerator before freezing. This helps it freeze faster and more uniformly, reducing damage to milk components.
  • Store milk in small 2-4 oz portions in milk storage bags, rigid plastic containers, or glass bottles designed for freezing.
  • Lay bags flat in the freezer to freeze faster. Bottles can go straight in.
  • Leave space in rigid containers as milk expands slightly when frozen.
  • Avoid using disposable bottle liners or regular plastic bags which can easily leak or tear.
  • Label bags or containers with date pumped and quantity before freezing.

Human milk stored in a deep freezer at 0°F is good for:

  • 6-12 months for a full-term healthy baby
  • 3-6 months for a preemie (less than 37 weeks)

The freezer compartment inside a refrigerator is okay for 2-3 weeks. For longer freezing, use a deep freezer or chest freezer set at 0°F or below.

Thawing and Warming Frozen Milk

Keep these safety tips in mind when thawing breast milk:

  • Thaw overnight in the refrigerator, holding for up to 24 hours. Gently swirl to mix any cream before use.
  • You can also thaw in a container of warm water, changing water every 15 minutes until thawed and warmed. Use within 1-2 hrs.
  • Do not thaw at room temperature or in hot water due to bacteria risk.
  • Avoid using the microwave which can create hot spots and alter components. However, some slow-thaw appliances designed for milk are okay.
  • Gently roll or swirl bottle to evenly distribute warmth and mix contents. Never shake or vigorously boil.
  • Once warmed, do not refreeze or refrigerate again. Use any leftovers within 2 hours.

With safe handling, breast milk retains its nutrient composition remarkably well and can be the exclusive milk source for baby for 6 months or longer. Storing milk properly gives you the flexibility to keep feeding breast milk even when you cannot nurse directly.

Choosing the Right Bottles for Pumped Breast Milk

When selecting bottles to store pumped milk, the most important factor is avoiding chemical leaching. Opt for:

  • BPA-free plastic bottles: Look for brands that clearly state BPA-free or made from safer polypropylene plastic. Avoid old, scratched bottles which may leach chemicals easier.
  • Glass bottles: Borosilicate glass bottles don’t interact with contents. Opt for an airtight cap and sleeve to prevent breakage.
  • BPA-free storage bags: Lay flat to freeze for efficient space use. Choose thicker bags designed specifically for breast milk over regular storage bags.

Key features to look for include tight sealing caps or lids, ability to withstand freezing and thawing, and durable, leak-proof construction. Wide openings allow easy cleaning. Bottles with ounce/milliliter markings help track quantities pumped.

Here are some good bottle options for storing breast milk:

Bottle Key Features
Philips Avent Natural Baby Bottles – BPA free polypropylene plastic
– Leak-proof double valve
– Wide bottle neck
Dr. Brown’s Glass Bottles – Borosilicate glass
– BPA-free components
– Vent system to limit air bubbles
Lansinoh Breastmilk Storage Bags – Double zip-seal top
– Stand and pour spouts
– BPA and BPS-free thick plastic

Proper Cleaning and Sterilization of Milk Bottles

Careful washing and sterilization of milk storage containers helps destroy illness-causing germs. Follow these steps:

  1. Wash hands thoroughly before handling pump parts and bottles.
  2. After each use, take apart bottles and wash all parts that contact milk in hot soapy water. Use a clean bottle brush.
  3. Rinse thoroughly with hot water to remove residue.
  4. Sterilize using one of these methods:
    • Steam sterilizer – Follow product instructions.
    • Boiling water – Fully submerge bottle and parts in boiling water for 5 minutes.
    • Steam – Hold bottle neck down over steaming water in a pot for 5 minutes, keeping neck out of water.
  5. Air dry fully before re-assembling bottles. Do not towel dry.

Deep clean pump parts at least once daily. Clean bottles after every use. Sterilize once daily or more if desired. Avoid using harsh dishwashing soaps which may leave residues.

Safe Bottle Feeding Tips for Expressed Breast Milk

When getting ready to feed your baby a bottle of your pumped milk, follow these safety guidelines:

  • Wash hands before handling milk.
  • Use milk removed from the refrigerator or freezer — never at room temperature.
  • Gently swirl milk to disperse cream before warming.
  • Warm milk gradually by placing bottle in warm water. Avoid microwaving.
  • Test temperature by dripping milk on your wrist before feeding. It should feel lukewarm, not hot.
  • Feed baby slowly, pausing often. Watch for cues like stopping sucking.
  • Throw out any milk remaining in bottle after feeding. Do not save or re-refrigerate.
  • Rinse bottle and parts immediately after use to avoid dried milk from sticking.

Proper warming helps retain nutrients in expressed milk. Sudden high heat from microwave ovens can cause hot spots that could burn baby.

Identifying Spoiled Milk

On occasion, stored breast milk can spoil before the recommended storage time. Look for these signs of spoiled milk:

  • Smell: Rancid or sour odor not like fresh milk
  • Color: Pink, yellow, or brown tint instead of white or cream
  • Texture: Separated, clumpy, gelatinous or slimy
  • Taste: Sour or bitter flavor

If milk shows signs of spoilage, err on the side of caution and discard it. Do not taste milk to check if unsure about appearance or smell.

Spoiled milk does not necessarily indicate your milk has “gone bad”. Certain components like fats may degrade faster, causing rancidity without making milk unsafe. But it’s not worth taking a chance on bacterial contamination.

Avoiding Contamination When Storing Milk

To help prevent spoiled milk, observe proper hygiene during pumping, storage, and feeding. Key tips include:

  • Always wash hands and pump parts before pumping sessions.
  • Use clean bottles meant for human milk storage.
  • Pump milk in a clean, dedicated space.
  • Seal bottles or bags tightly to avoid leaks or spills in freezer.
  • Store only breast milk in designated bottles. Do not mix with formula, juice, etc.
  • Freeze milk immediately if not using soon.

Bottles that appear clean may still harbor unseen contaminants. Sterilizing provides an added layer of protection against bacteria or viruses entering expressed milk, especially important for preemies.

Traveling With Expressed Breast Milk

You can transport refrigerated or frozen breast milk for your baby while traveling. Some tips for travel:

  • Carry frozen milk in a cooler with ice/cold packs to keep it as close to 0°F as possible.
  • Insulate bottles of refrigerated milk, like in a cooler bag. Limit opening/closing cooler.
  • Consider bringing a travel bottle warmer, or pack the milk close to an ice pack in the cooler to chill it faster.
  • Avoid checking frozen milk if flying — the flight may be longer than the 3-4 hour recommended max time milk should thaw.
  • When you arrive, immediately use refrigerated milk or put frozen milk in freezer.

It’s best to transport expressed milk in insulated coolers with ice rather than leave it in a hot parked car for extended periods. Try to keep milk as cool as possible during travel.

Storing Milk When Returning to Work

Going back to work while still breastfeeding means you’ll need to pump and store your milk. Here are some tips to make it go smoothly:

  • Speak to your employer about accommodations for pumping breaks and a private space with access to a power outlet and sink.
  • Discuss using the employee refrigerator to store milk with colleagues. Get a designated shelf or container.
  • Bring a portable cooler bag to transport milk home. Include cold packs or ice.
  • Label all milk clearly with name and date for work fridge.
  • Freeze any extra milk for later – this takes up less space.
  • Clean pump parts as soon as possible after each session to avoid lingering milk smells at work.

With planning ahead and thoughtful storage, you can continue providing your nourishing milk for your baby’s needs even after returning to work outside the home.

Common Pumping and Storage FAQs

Does breast milk last longer frozen or refrigerated?

Frozen milk lasts significantly longer than refrigerated, around 6–12 months in a deep freezer vs. 3–5 days in the refrigerator. Freezing is the best method for long-term storage.

Can I combine milk from different pumping sessions in one bottle?

It’s best to store milk in smaller portions of 2–4 oz. However, milk from two different sessions can be combined as long as it was pumped on the same day. Chill the fresher milk before combining.

Is it okay to freeze milk in disposable bottle liner bags?

No, disposable bottle liners are too thin and prone to cracking and leaking. Opt for thicker, durable breastmilk storage bags designed for freezing instead.

Can I microwave bottles of frozen milk to thaw or warm them?

Microwaving can lead to hot spots that could burn baby. It’s safer to gently thaw or warm milk under warm running water or in a warm water bath. Never boil or overheat.

How long can breastmilk sit out at room temperature?

Freshly pumped milk is good for 4 hours at room temperature up to 25°C or 77°F. Any longer than 4 hours, it’s best to refrigerate or freeze the milk right away.

Do I need to sterilize pump parts and bottles before each use?

You don’t necessarily need to sterilize every time. A thorough wash with hot soapy water is sufficient for cleaning before each use. Sterilizing everything once daily provides added protection.


Storing breast milk properly is important so your hard work and nutrition is not wasted. When pumped and stored using the proper containers, temperatures, and handling, breast milk retains its nutritional and immune-boosting qualities to continue providing optimal nourishment for your baby, even when you cannot breastfeed directly. With safe refrigeration and freezing, storage is convenient and flexible whether at home, work, or on the go.

Leave a Comment