Pumping Exclusively: How To Store Breast Milk Safely

As a first-time mom, I wish I had known how to store breast milk after pumping before my baby arrived! The day I came home from the hospital with a newborn, I was so overwhelmed.

I assumed my baby would naturally know how to latch onto the breast, but instead, I had to quickly figure out how to assemble the breast pump and store breast milk correctly.

It was a lot to handle!

I had no idea there were so many rules about storing breastmilk to prevent it from going bad. I spent a lot of time on Pinterest and Google trying to figure it out. After successfully pumping exclusively for 14 months, I think I can say I know how to store breast milk!


I’m here to share the most straightforward step-by-step guide to storing breast milk after pumping, something I wish I had when I was pumping.

How to store breast milk safely

Table of Contents

How To Store Breast Milk After Pumping

Step 1: Learn The Optimal Storage Temperatures

Room Temperature

Freshly expressed breast milk can be stored at room temperature for up to 4 hours (ideally between 60-75°F or 15-24°C). Discard any milk left at room temperature beyond this timeframe.


Breast milk can be stored in the refrigerator for up to 4-6 days at temperatures of 32-39°F (0-4°C). Placing it towards the back of the fridge, away from the fridge door, maintains a more consistent temperature.

It’s best to use it within the first few days for optimal freshness. Leftover milk can also be refrigerated but only up to 2 hours after feeding.


Breast milk can be stored in the freezer for an extended period. In a standard freezer compartment within a refrigerator, it can last for about 3-6 months. Store milk in small amounts (2 to 4 ounces) to avoid wasting any.

Deep Freezer

At 0°F (-18°C) or lower, it can last for up to 6-12 months. Ensure proper labeling with the date of expression to keep track of storage time and prioritize using the oldest milk first (first in, first out)

Insulated Cooler Bags

Use an insulated cooler bag with ice packs to keep the milk at a safe temperature. Place ice packs around the milk containers. Make sure the ice packs are frozen before you leave. The breast milk should be kept at a temperature of 39°F (4°C) or below.

If possible, check the temperature periodically. Keep the cooler bag out of direct sunlight to help maintain the temperature inside. Breast milk can be stored safely in an insulated cooler bag with ice packs for up to 24 hours. 

Handling Tips

If possible, chill the cooler bag and ice packs before placing the breast milk inside. Try to minimize the number of times you open the cooler bag to keep the temperature consistent.

Transfer and Use

Once you reach your destination, place the breast milk in a refrigerator or freezer as soon as possible. If any milk has thawed, it should be used within 24 hours and not refrozen.

*Resources: CDC Breastfeeding Storage Guidelines & La Leche League International Storing Human Milk

Step 2: Choose a Storage Container

breast milk storage options

 a. Bottles

Use BPA-free glass bottles or hard plastic. Ensure the bottles are clean and sterilized before use. Bottles are a great storage option when you know you’ll use them within the following two feeds because they’re ready to go. 

b. Breast Milk Storage Bags

When it comes to longer storage, breast milk storage bags are your practical and space-saving solution. These bags, specifically designed for storing breast milk, are not only convenient for freezing but also ensure the safety of your milk with their sturdy and secure seal, preventing any leakage. 

Breastmilk storage bags are great for storing breastmilk for the next few days, whether that’s in your fridge or the back of the freezer, or while on the go, whether that’s at work, in your car, or at an airport, because they are easy to store in a travel bag with ice packs. 

c. Pitcher

Pitchers are a good storage option for pumping moms with a large milk supply who prefer to mix their daily milk supply together for easy access. Be sure to clean containers before use.  

Beware: You can’t mix fresh milk with cold milk. Because of this, I would just put it in bags so I didn’t have to worry about milk temperatures. But do what works for you

Step 3: Learn to Correctly Label and Date Stored Milk

Labeling your breast milk allows you to keep track of its age, ensuring that you use the oldest milk first to minimize waste. Knowing when the milk was expressed helps you follow storage guidelines and prevents feeding expired milk to your baby. Additionally, recording the time of expression enables you to monitor your pumping schedule and milk production patterns.

Use Waterproof Markers

Use a waterproof marker to write on the breast milk storage bags. These markers resist smudging and fading when they come into contact with moisture. This is crucial for maintaining clear information throughout storage and thawing, especially for breast milk safety.

Ensure Clear and Legible Labeling for Easy Identification

Write the date and time of expression in a legible manner to avoid confusion. Optionally, you can include other relevant information such as the volume of milk, your baby’s name, or any special instructions for caregivers.

Step 4: Learn How To Thaw Breast Milk Safely

Thawing frozen breast Milk options

Thawing Option 1: Thawing Breast Milk in the Refrigerator Overnight

Thawing breast milk in the refrigerator is the safest method, allowing for a slow and controlled thawing process. It’s a good idea to plan ahead by transferring the frozen breast milk from the freezer to the refrigerator the night before it’s needed to ensure it’s fully thawed when needed.

Thawing breast milk in the fridge helps maintain its nutritional quality and minimizes the risk of bacterial growth.

Thawing Option 2: Using Warm Water to Thaw Frozen Breast Milk Quickly

If you need to thaw breast milk more quickly, you can use warm water. Fill a clean container with warm (not hot) water. Place the frozen breast milk container (bottle or storage bag) in the warm water bath, ensuring it’s fully submerged.

Rotate the container occasionally or change the warm water to maintain a consistent temperature until the milk is fully thawed.

Step 5: Learn to Gently Swirl Milk Layers after Thawing (Not Shaking)

Breast milk may separate into layers during storage, with the cream rising to the top. After thawing, gently swirl or rotate the container to mix the milk layer together.

Avoid vigorous shaking, which can damage the milk’s delicate proteins and nutrients. Gentle mixing helps ensure an even distribution of fats and nutrients, providing your baby with a consistent and nourishing feeding experience.

Step 6: Learn to Warm Breast Milk Safely 

Warming Breast Milk options after pumping

Warming Option 1: Using a Bottle Warmer to Warm Milk

Using a bottle warmer is a convenient way to warm breast milk. Please read the manufacturer’s instructions before using it. Ensure the parts are clean and assembled correctly. Add the required amount of water and place the bottle in the warmer. Turn it on and monitor the process. Once warmed, gently swirl the bottle to mix the milk. Avoid shaking it vigorously.

Warming Option 2: A Bowl of Warm Water 

The best way to warm breast milk stored in a storage bag is in a bowl of warm water. As mentioned in the thawing process, you simply place the thawed milk in warm water and let it sit until it’s warm enough to drink. Simple.

Avoiding Microwave Heating to Prevent Hot Spots and Nutrient Loss

Heating breast milk in the microwave is not recommended as it can create uneven heating and hot spots, which can scald your baby’s mouth.

Microwave heating can also lead to nutrient loss in breast milk, reducing its nutritional value for your baby. Stick to safer thawing and warming methods, such as using warm water or a bottle warmer.

Avoid These Common Milk Storage Mistakes

Avoid these common storing breast milk mistakes

1. Overfilling Storage Containers

Avoid filling storage containers to the brim to allow for milk expansion during freezing. Overfilling can cause containers to break or leaks.

Many breast milk storage containers have designated fill lines to indicate the maximum volume for safe storage.

2. Not Properly Sealing/ Closing Container of Choice

Make sure to use tight-fitting lids or seal to prevent air exposure and maintain milk quality. Before storing breast milk, inspect containers for any cracks or gaps in the seal that could lead to leaks or contamination.

For added protection, consider using containers with double-sealing mechanisms or additional sealing layers such as zip-lock bags.

3. Not Using the Oldest Milk First

Always organize stored breast milk based on the date of expression, placing the oldest milk at the front or top for easy access. Prioritize using the oldest milk first to ensure your baby receives the freshest milk available.

Periodically review your stored milk inventory to ensure older milk is used before it reaches its expiration date.

4. Not Checking Milk for Signs of Spoilage Before Feeding 

Before feeding, smell the breast milk to detect any sour or off odors, which may indicate spoilage. Examine the color and consistency of the milk. Fresh breast milk is typically white or bluish-white with a smooth consistency.

Discard milk that appears discolored or has unusual textures. If you have any doubts about the safety or quality of stored breast milk, err on the side of caution and discard it.

5. Storing Milk on the Fridge or Freezer Door

Always store milk in the back of the refrigerator or freezer to prevent it from going bad due to the changes in temperatures every time the door opens. 

6. Mixing Milk of Different Temperatures Togther 

If you are adding freshly pumped milk to already stored milk, ensure both are at the same temperature (e.g., cool the freshly pumped milk in the refrigerator before adding it to a refrigerated batch).

Last Thoughts

Storing breast milk correctly ensures your baby receives the best nutrition even when you’re not around. Mastering the storage process can seem overwhelming for new pumpers, but with these guidelines, you can confidently preserve your milk’s quality.

Additionally, don’t hesitate to seek the support of a lactation consultant if you have any questions or concerns. They can provide personalized advice and practical solutions to smooth your pumping and storage journey.

Continue to nurture and nourish your little one with confidence. Happy pumping!

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