How To Master Pumping Breast Milk: Breastmilk Storage Guidelines – Part 4

A nurse midwife and mama of four reviews guidelines for safe breastmilk storage

some guidelines on breastmilk storage
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This is a series on how to master pumping breast milk. You can read the other articles of the series here:

Not sure how to thaw, freeze, or otherwise store your breastmilk? This article will cover all you want to know about breastmilk storage guidelines— how much, how long, and what to store it in.

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As a Certified Nurse-Midwife with four kids who works 24-hour shifts, I am not always sure when my next opportunity to pump will be.

Concerned that my milk would go to waste with my hectic schedule, I made it an absolute priority to familiarize myself with the guidelines for breastmilk storage.

In my quest for freezer knowledge, I learned that freshly expressed milk is the priority. If you just pumped, your baby will get the most health benefits from that bottle over a frozen bag in your stash.

If you aren’t going to use milk in the next four days, freeze it. I learned to label my milk because throwing away breastmilk is heartbreaking.

If you are pumping your breasts for any reason, you want to store the liquid gold that you have saved!

Breastmilk can be stashed in an insulated lunch bag, your fridge, the freezer, or kept at room temperature.

However, the length of time that each storage option is safe for, varies.

How do I Store Breastmilk?

First, when storing breastmilk, make sure that you have washed your hands with soap and water.

The other important consideration is what type of storage you will need. Do not use sandwich bags!

These are very likely to leak and breakdown, wasting your precious milk.

When it comes to milk storage, you have several options

  • Breastmilk storage bags. Remember that liquids expand upon freezing! If you leave space at the top of the container, you may be able to keep your precious milk from spilling.
  • Glass baby bottles with spill-proof lid. These are incredible for the planet and your baby, but they do not fit well in the freezer. Glass bottles are often large, inflexible, and the shape does not fit well with other freezer storage containers.
  • BPA-free plastic bottles. You may run into the same issues as with glass bottles. Your freezer will quickly overflow if you use these.

Consider how much storage you have in your freezer when selecting your storage medium.

With breastmilk bags, squeeze out all the air and lay them flat in your freezer. When storage bags are frozen, you can stack them in a large freezer bag or shoe box to organize them.

Place the oldest milk in the front so you will always use the oldest milk first.

Once you’ve placed your milk in a container, write the date and time with a clear label. You want to use up the oldest first.

Use the table below if you’re unsure how long milk will stay fresh. Place your milk in the coldest part of your refrigerator or freezer.

Do not put it in the door as the liquid slightly warms every time you open the appliance. You don't want early spoilage of your liquid gold!

The Centers for Disease Control (CDC) recommends avoiding any plastic storage with the recycle symbol number 7, this may indicate toxic BPA-containing plastic.

How Much Milk Should I Store?

The best practice for saving your milk is to store a variety of different size feeds so that you can pull the amount you estimate that your baby will need.

If you make bags that are too big or too small, you may wind up wasting time or breastmilk. Guess the amount of milk your baby drinks in one sitting.

Freeze containers in that range, but if you have to guess, smaller portions are better than larger bags to minimize waste.

In the first few weeks, when the baby’s tummy is small, freeze 60 to 90 ml (2-3 oz) in one bag.

From that point on, anywhere from 90 to 150 ml (3-5 oz) may be appropriate, depending on your baby’s appetite and how much he feeds.

Does Frozen Breastmilk Lose Health Benefits?

guidelines on how to store breastmilk
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Yes, but only for certain vitamins and minerals, like vitamin C. The total protein and fat content, Vitamins A, B, and E, and immunoglobulins for immunity remain available for babies at three months after freezing.

The longer you store breastmilk, the more vitamins, and antioxidants that you lose.

However, it still has more health benefits than formula. Human breastmilk is the best option, if possible, whether it is fresh or frozen.

How Can I Thaw or Warm My Milk?

Place the milk storage unit in a cup of warm water. Test the breastmilk on the inside of your wrist to make sure that it’s not too hot for your baby.

Do not microwave your breastmilk directly! Boiling milk in the microwave unevenly heats liquids and creates areas with hot pockets that may scald your baby’s mouth.

The other reason is that boiling milk reduces some of the health benefits.

After your baby is a few months old, many babies will take chilled bottles from the refrigerator.

When thawing your milk, you can place frozen milk in the fridge the night before using it. Once it is out of the freezer, plan to use it within 24 hours.

If you’ve run out of thawed milk, heat breastmilk slowly in a cup of warm water before giving to your baby just like you are warming it above.

Remember to test it to make sure it’s not too hot!

Is it Safe to Mix Breastmilk From Different Pumping Sessions?

Yes, as long as you cool both fluids before combining. Do not add the warm breastmilk to the cooled milk in the fridge. Write the date/time of the oldest milk on the storage piece.

How Long can I Store Breastmilk?

Breastmilk Storage Guidelines from the CDC help us understand how long we can store breastmilk in different situations

Human Milk Storage Guidelines
Storage Locations and Temperatures
Type of breastmilkCountertop 77°F or colder (25°C) (room temperature)Refrigerator 40°F (4°C)Freezer 0°F or colder (-18°C)
Freshly Expressed or PumpedUp to 4 hoursUp to 4 daysWithin 6 months is best
Up to 12 months is acceptable
Thawed, Previously Frozen1-2 hoursUp to 1 day (24 hours)Never refreeze human milk after it has been thawed
Leftover from a Feeding (baby did not finish the bottle)Use within 2 hours after the baby is finished feeding
Adapted from "ABM Clinical Protocol #8: Human Milk Storage Information for Home Use for Full-Term Infants," Revised 2017 External.

What is the Soapy Smell to My Milk?

Lipase is an enzyme in human breastmilk that makes babies turn up their nose. In some cases, the milk may spoil more quickly.

If you notice a soapy smell to your breast milk and find that baby won’t finish a bottle after freezing, consider that you may have high levels of lipase in your breastmilk.

The recommendation is to scald the milk before freezing it to deactivate the enzyme.

To scald your milk, place a pot of breastmilk on the stove until bubbles barely form at the edges, then let the milk cool and put it in the freezer.


Breast pumping enabled me to give my little ones my breastmilk exclusively until one year old.

It saved my breastfeeding relationships with my children while I maintained an incredible career. It’s hard work, and it can be frustrating at times.

By following the breastmilk storage guidelines I explained in this article, you will be able to store your nursling’s breastmilk properly.

some guidelines on breastmilk storage
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Written by Caitlin Goodwin

Caitlin Goodwin is a board certified nurse-midwife, runs the family travel and autism blog, Typically Twitterpated and is a mom to four children. In her spare time, she and her family follow a gluten-free diet and share a love of all things travel, especially Disney.