Every drop of breast milk represents time, effort, and love. Making sure it's stored safely means your baby gets to benefit from every bit of it. Whether you're pumping at work, or just trying to figure out the best way to organize what you've got, having a simple, reliable storage system makes a real difference. Here's what you need to know, from choosing the right bag to knowing when it's time to let a bag go.

Following safe storage guidelines helps protect the quality and safety of your milk. According to the CDC and ABM Clinical Protocol #8, here’s what’s recommended for healthy, full-term babies:

There are a few helpful things to keep in mind when it comes to milk storage. Write the date and volume on the storage bag. Store milk in the main compartment of the refrigerator or freezer, and preferably in the back. Storing milk in the door is not recommended as temperatures tend to fluctuate more due to opening and closing. When you’re traveling, milk can be kept in an insulated cooler with ice packs for up to 24 hours. It’s important to note that if your baby is premature or if they have any health considerations, to check with your pediatrician as guidelines may differ.

Thawing and Using Frozen Milk

To thaw milk, the easiest method takes a bit of planning. Simply move the bag from the freezer to the refrigerator the night before where it can thaw gradually and safely overnight. For faster thawing, place the sealed bag under lukewarm water in a bowl or under running water. An important tip is to never microwave breastmilk. This can create uneven hot spots that can burn your baby’s mouth, even if testing it on your arm feels fine. 

Once the milk is thawed, use within 24 hours if it was thawed in the refrigerator and use within 1-2 hours if it was warmed up or brought to room temperature. Always use the first in, first out. Also, if your stored milk looks or smells a little different than your fresh milk, don’t panic! Fat separation is normal, just swirl to recombine. Some moms may notice a soapy smell. This can be due to an enzyme called lipase, which is a natural variation in milk composition and not a safety concern. 

When to Toss Milk

It's never easy to pour out milk you worked hard for, but when in doubt, it's always okay to err on the side of caution for your baby's safety. You should discard the milk if it’s been thawed and warmed but not finished within two hours or if it smells sour or rancid. This is different from the soapy smell, so when in doubt, ask your IBCLC. 

A common question is if you can refreeze milk.  Previously frozen milk that has been thawed should not be refrozen. Once it's thawed, the clock is running, use it within the timeframes above. If the milk is not completely thawed, you can put it back in the freezer. 

Choosing the Right Size Bag

This might seem like a small detail, but it actually matters more than you'd think. Six ounce bags are most commonly seen on the market right now. A bag this size can be a great fit if you’re consistently pumping more per session, or if you’re combining sessions. Amaris has released three ounce milk storage bags, which can be a wonderful option for many moms. Pumping sessions can vary so much from person to person, and even day to day. Storing milk in a bag that matches what you’re actually pumping can be helpful. Sometimes the visual of a half empty bag can feel discouraging, even when your output is completely normal and enough for your baby. Using a storage bag that fits your needs can help you see your milk accurately and feel good about what you’re storing. Neither size is better than the other, it’s about what works for your body and your routine. For this reason, Amaris also has milk storage bags in the six ounce size. 

What Makes These Bags Worth It

The storage bags from Amaris were designed with real pumping moms in mind, because the details matter when you're handling something this precious. Some features include a double zipper seal for extra leak protection, and an easy pour spout on the side which allows you to transfer directly into a bottle without the mess. They also include fun and encouraging designs because pumping is hard work, and a little joy along the way goes a long way. Another great thing about these bags is the lay flat freezing design, which brings me to our next storage tip. 

To maximize space, freeze your milk bags flat in the freezer. Once bags are frozen solid, you can store them upright like files in a bin or box for easy organization and quick access. Always label each bag with the date, time, and amount so you can use the oldest milk first.

A Simple System That Works

The combination of the right size bag, a lay-flat freezing method, and clear labeling can make your entire storage routine feel so much more manageable. You've done the hard work of pumping so a good system makes sure none of it goes to waste.

And if you ever have questions about your storage setup, milk output, or anything else along the way, an IBCLC (International Board-Certified Lactation Consultant) is always a great resource for personalized support.

Sources: Centers for Disease Control and Prevention. (2026). Breast Milk Storage and Preparation. https://www.cdc.gov/breastfeeding/breast-milk-preparation-and-storage/handling-breastmilk.html

Eglash, A., Simon, L., & The Academy of Breastfeeding Medicine. (2017). ABM Clinical Protocol #8: Human Milk Storage Information for Home Use for Full-Term Infants, Revised 2017. Breastfeeding Medicine, 12, 390–395. https://www.bfmed.org/assets/DOCUMENTS/PROTOCOLS/8-human-milk-storage-protocol-english.pdf