How do you store milk after pumping?

When it comes to storing breast milk after pumping, it’s important to follow proper guidelines to ensure the milk stays fresh and retains its nutritional value. Proper storage is key for providing your baby with the benefits of breastmilk for as long as possible.

Quick Tips for Storing Pumped Milk

Here are some quick tips to keep in mind when storing pumped milk:

  • Store milk in clean bottles or storage bags designed for breastmilk.
  • Label the milk with the date it was pumped.
  • Store small amounts (2-4 oz) to avoid waste.
  • Use milk within 3-5 days if storing in the refrigerator.
  • Store in the back of the fridge, not the door.
  • Freeze milk if storing longer than 5 days. Frozen milk can be stored for 6-12 months.
  • Limit repeated thawing and re-freezing as it can affect quality.
  • Refrigerate or chill milk right after pumping. Don’t leave at room temperature.
  • Store milk in 2-4 oz portions to thaw quickly.
  • Thaw frozen milk in the refrigerator or by running it under warm water.

How to Store Freshly Pumped Breast Milk

Here are some common guidelines for storing freshly pumped milk:

Room Temperature

Freshly pumped milk can sit at room temperature (up to 77°F) for:

  • Up to 4 hours if pumped in a very clean environment
  • Up to 3 hours if pumped in a standard environment
  • 1-2 hours if pumped in a communal or non-sanitized environment, like a shared pump room

It’s best to refrigerate or chill milk sooner if possible.


Store pumped milk toward the back of the refrigerator (not the door) at a temperature of 39°F or below. Milk can be stored for:

  • Up to 4 days if fresh
  • Up to 3 days if previously frozen


For long term storage, freeze breast milk in a freezer set to 0°F or below. Stored frozen, milk can last:

  • 6-12 months in a deep freezer (-4°F)
  • 6 months in a self-defrosting deep freezer
  • 3-6 months in a refrigerator/freezer with separate doors
  • 2 weeks in a combination fridge/freezer

How to Store Thawed Breast Milk

Previously frozen milk that has been thawed can be stored:

  • In the fridge for up to 24 hours
  • At room temperature for up to 2 hours

Do not refreeze thawed milk unless it was left chilled in the refrigerator. Avoid re-freezing thawed milk more than once as it can break down cell walls affecting nutrition.

Proper Bottles and Storage Bags for Pumped Milk

It’s important to store pumped milk in containers designed specifically for breastmilk. Options include:

  • Breastmilk storage bags – These are made from food-grade plastic and designed to fit neatly in freezers. Choose those with secure seals to avoid leakage.
  • Plastic bottles – Opt for BPA-free plastic bottles with tight sealing lids. Bottle sets with connectors for pumping directly into storage are convenient.
  • Glass bottles – Glass prevents chemicals from leaching but is heavier and can break. Use bottles with secure lids.

Bottles and bags should be washed in hot soapy water or a dishwasher before first use. Air drying is recommended over towel drying.

Labeling and Organizing Stored Milk

To avoid confusion and waste, always label milk containers with:

  • The date milk was pumped
  • The number of ounces inside

You may also want to make note of any medications taken or contents that may affect the milk, like caffeine.

When freezing milk, organizing oldest milk to be used first is key. Systems that can help include:

  • Putting newest milk in the back of the freezer and using oldest in front first
  • Placing milk in dated milk storage boxes
  • Using labels or stickers noting the date the milk was pumped

Thawing and Warming Stored Breast Milk

The safest ways to thaw and warm stored milk are:


  • In the refrigerator overnight
  • Under cool running water for a quick thaw
  • Never thaw at room temperature or in hot water


  • Under warm running water
  • In a bowl of warm water
  • Gently in a bottle warmer

Avoid microwaving milk directly as it can create hot spots that scald milk. Swirl thawed milk gently before feeding and smell for any sourness before giving to baby.

How Long Does Unrefrigerated Pumped Breast Milk Last?

Pumped breast milk that is left unrefrigerated starts to break down quickly. Here’s how long pumped milk typically lasts if left out:

Room Temperature Duration
Up to 77°F (25°C) 3-4 hours
78-82°F (26-28°C) 2 hours
Over 90°F (32°C) 1 hour or less

As a general rule of thumb, the warmer the milk, the less time it can safely sit before refrigeration. It’s best to chill milk as soon as possible after pumping.

Can Refrigerated Breast Milk be Left at Room Temperature?

Previously refrigerated milk should not be left out at room temperature for long periods. Here are temperature guidelines:

  • At 77°F or colder – Up to 4 hours
  • 78-82°F – Up to 2 hours
  • Over 90°F – 1 hour or less

The milk needs to return to the refrigerator as soon as possible. The total time at room temperature (including initial pumping time) should not exceed 3-4 hours total.

Should Pumped Milk Smell Bad or Change Colors?

Properly stored pumped milk should have little to no odor. It is normal for the milk to take on a bluish, greenish white color as it ages but drastic color changes are not normal. Here are some signs milk may be spoiled:

  • Curdled consistency
  • Sour or rancid smell
  • Pink or red tint
  • Greyish color
  • Mold visible

If milk smells odd or shows any signs of spoilage, err on the side of caution and do not feed to baby. Remember, smell and taste breast milk before serving after storing.

Can You Refreeze Thawed Breast Milk?

Previously frozen milk that has been thawed can be refrozen but there are a few guidelines to follow:

  • Only refreeze milk that was thawed in the refrigerator, not at room temperature or in hot water.
  • Refreeze milk within 24 hours of thawing.
  • Limit re-freezing thawed milk to one additional freeze.
  • Make sure milk was stored in appropriate freezer bags or containers.
  • Clearly label milk was previously frozen when re-freezing.

Milk expands when frozen so be sure to leave room in the storage container. Thawing and re-freezing milk too often can impact cell integrity and nutrition but occasional refreezing of chilled milk is considered safe.

Can You Combine Fresh and Thawed Pumped Milk?

It is safe to combine fresh milk with chilled thawed milk if done properly. Follow these steps:

  1. Fully chill freshly pumped milk in the refrigerator.
  2. Chill thawed milk completely in the refrigerator after warming.
  3. Combine the chilled fresh milk and chilled thawed milk.
  4. Use the milk within 24 hours.
  5. Do not re-freeze combined milk.

Only mix cooled, chilled milk. Never add warm fresh milk to thawed chilled milk as it reduces the overall chilled temperature.

Does Pumped Milk Separate When Stored?

It is normal for breastmilk to separate into layers when stored. This is due to the different components in milk:

  • Cream: Rises to the top layer and looks thicker.
  • Foremilk: Remains on the bottom and looks thinner.

Separation does not mean the milk is spoiled. Gently swirl, rather than shake, milk to remix the layers before feeding. The storage fat in milk will help baby feel full.

Can You Store Breast Milk in the Freezer Door?

Storing pumped breast milk in the door of the refrigerator freezer is not recommended. The door is the warmest part of the freezer due to temperature fluctuations from opening. This can compromise milk nutrition and freshness.

For best results, store breast milk toward the back rather than the door of the freezer. The back of the freezer maintains a more consistent freezing temperature keeping milk fresher for longer.

What are the Best Breast Milk Storage Bags?

The best breastmilk storage bags:

  • Are made from food-grade BPA-free plastic
  • Have a double zipper or tight closure to prevent leaks
  • Are puncture and tear-resistant
  • Have clear labeling areas to date and track milk
  • Lay flat for easy stacking and freezing
  • Come pre-sterilized or are dishwasher safe

Top choices include Medela, Lansinoh, Kiinde, Dr. Brown’s, and Philips Avent breastmilk storage bags. Compare features to choose bags that best suit your needs and budget.

How Many Ounces per Breastmilk Storage Bag?

Breastmilk storage bag ounces recommendations:

  • 2-4 ounces for freezing – Smaller portions thaw faster.
  • 3-6 ounces for refrigerating – Use what baby would take in one feeding.
  • 12+ ounces for longer storage – Minimize waste if pumping abundant milk.

Aim for smaller volumes for freezing and enough for a feeding session when refrigerating. Too much milk in bags can increase waste if baby doesn’t finish.

Can You Pump Directly into Breast Milk Storage Bags?

Pumping directly into storage bags is possible with the right adaptors or pump flanges designed for the bags. However, some potential risks include:

  • Overfilling bags can cause leakage and contamination.
  • Milk can be difficult to evenly freeze in upright bags.
  • Connecting pieces must be thoroughly cleaned and sanitized.
  • Freezing expandable plastic bags can cause punctures.

For best results, pump into bottles first before dividing into storage bags. But pumping into bags can help minimize transfers and extra parts to wash.

How Many Breast Milk Storage Bags Do You Need?

The number of breastmilk storage bags needed depends on your pumping frequency and output. Here are some estimates:

  • 24-48 bags for occasional pumping 1-2 times per day
  • 50-100 bags for pumping 2-3 times per day
  • 100+ bags for exclusive pumping several times per day

Buy bags in bulk or multi-packs for cost savings. Having 50-100 bags on hand avoids running out before you can buy more. Extras allow freezing in smaller volumes.

Do Breast Milk Storage Bags Leak?

Well-designed breastmilk bags should not leak, but leaks can happen occasionally due to:

  • Overfilling – Leave space at the top for milk to expand.
  • Improper sealing – Double check zippers are fully closed.
  • Freezer burn – Use milk before 6-12 months and minimize openings.
  • Accidental punctures – Inspect bags carefully before filling.
  • Poor quality – Choose thicker grade bags from reputable brands.

Gently lay filled bags flat in the freezer to prevent leaking from popsicle-like expansions upright. Avoid contact with sharp freezer edges or placing heavy items on frozen bags.

Do Breast Milk Bags Need to Be Sealed Before Freezing?

Sealing breastmilk bags before freezing is strongly recommended. Reasons to properly seal bags include:

  • Prevents spills, leakage, and contamination.
  • Minimizes oxygen exposure to better preserve nutrients.
  • Avoids freezer burn which can damage milk fats.
  • Reduces risk of absorbing freezer odors.
  • Allows stacking bags cleanly and neatly.

Fully expel excess air and run your finger along the zipper seal to close bags tightly before freezing. Double check for leaks by flipping bags upside down before freezing.

Can You Freeze Breast Milk without Bags?

Breast milk can be frozen without storage bags in a pinch, but it carries some drawbacks:

  • Harder to stack neatly and organize in freezer
  • More exposed surface area can cause freezer burn
  • Higher risk of contamination from other foods
  • Possibility of spilling during transport
  • Difficult to label date and amount

If freezing without bags temporarily, use very clean, sealed containers clearly labeled for breast milk. Freeze for only 2-4 weeks before transferring to bags for long term storage.


Following proper storage guidelines maximizes the nutritional content in expressed breast milk for baby. Refrigerating right after pumping, avoiding contamination, freezing in small batches, and labeling milk properly helps it stay fresh and safe for feeding. Choosing the right breastmilk bags or containers suitable for freezing and thawing also makes storing smooth and organized. With the right techniques, you can preserve your breast milk to provide all the invaluable benefits to your little one for months to come.

Leave a Comment