Build Your Freezer Stash Of Breastmilk: The Ultimate Guide To Stockpiling And Storing Milk

storing and freezing breast milkWhile feeding breastmilk from boob to mouth is pretty straightforward, there are safety guidelines to follow if you bottle feed expressed milk. Parents who feed formula will know most of these tips, but for those of you who breastfeed, here are the correct storage times, methods, and temperatures for handling pumped milk.

How long can I keep expressed breast milk at room temperature?

Freshly expressed milk can be kept in its original collection bottle for 3-8 hours at room temperature (under 85 degrees Fahrenheit). This is assuming that you haven’t touched the milk and that it is kept with a lid on, out of direct light, and away from heat. If it is hotter than 85 degrees where you are, then you should only keep the milk unrefrigerated for about 2-4 hours.

How long can I keep breast milk in a cooler?

The interior of the cooler should be kept at 65 degrees Fahrenheit or lower. Make sure your cooler does not have any leaks and place the ice pack as close to the bottle of milk as possible. Direct contact between the ice pack and milk is best. At this temperature, the breast milk can be kept for up to 24 hours. This is more than enough time for working moms who pump at the office. You should transfer the milk to the refrigerator or into the freezer as soon as you get home.

The working mom’s guide to using a breast pump

How long can I keep breast milk in the refrigerator?

Refrigerated breast milk can be stored for up to 8 days. Even though you can keep breast milk in the fridge for that long, it is best to use it up in 3 days and to transfer any milk that you can’t use in the next couple of days to the freezer.

Make sure you label your milk containers with the date when the milk was pumped. Use up the oldest milk first and keep the milk near the back of your refrigerator where temperatures are the coolest. Do not store breast milk in your fridge door or near the front as the temperature will rise every time you open the door.

How long can I keep breast milk in the freezer?

Breast milk can be kept in a sealed and air tight container and frozen for up to six months.

A tightly sealed container or storage bag is necessary to prevent problems with freezer burn and off flavors.

Do not overfill your bottle or storage bag as they will burst and leak when you thaw out the milk.

If possible, use up frozen breast milk within 3 months as that is when the fats in the milk will start to go rancid and nutrients such as vitamin A and vitamin C decrease.

My reviews of the best electric breast pumps

Breast milk storage times chart

Breast Milk Storage Times Chart

What are the best storage containers for breast milk?

There are three types of storage methods for pumped milk.

  • collection bottles
  • storage bags
  • milk trays

Collection bottles  (Amazon | buybuybaby) are the easiest to use and the best choice for moms who pump infrequently. Your milk is pumped directly into the bottle and you just have to pop a lid on top and store the milk in a cooler or refrigerator. Then when it’s time to use the milk, just screw on a teat, warm on the milk, and you’re ready to feed.

On the other hand, bottles take up a lot of space, have to be kept upright, and are easy to mix up. That’s why they’re only practical for a couple days/bottles of milk. Label each bottle with a sticky note with the date the milk is expressed and remember to use up the oldest milk first. You can also use a bottle organizer  (Amazon) to help you keep track of which bottle is the newest/oldest.

If you plan on freezing your breast milk and building up a supply for emergencies, storage bags and milk ice cube trays are a better idea.

Breast milk storage bags (Amazon | buybuybaby) are like ziploc bags designed especially for breast milk. They are designed to be sterile and to not leak, so don’t think you can replace them with regular ziploc bags!

Some storage bags can be used with your breast pump, letting you express directly into the bag. The usual method is to express into a collection bottle and then pour the milk from the bottle into a bag.

If you’re pumping away from home, it’s best to just keep the milk in the collection bottle and wait until you get home to decant the milk into a storage bag. It’s just less messy and more hygienic this way.

Milk storage bags are perfect for the refrigerator or for freezing. They stack up nicely once they are filled and sealed and if you get a breast milk storage bag organizer, it’s like having a file cabinet of breast milk packets at your fingertips.

You’ll still want to label each bag with the date the milk was expressed. Use a soft tip marker so you don’t puncture the bags and stack them so the oldest milk is at the front.

If you plan to freeze your breast milk, line them up in a breast milk storage bag organizer (Amazon | buybuybaby) or box so they don’t freeze into funny shapes.

Try not to overfill the bags (they’re usually designed to hold 1 oz-2 oz) as the breast milk will expand when frozen and tear the bags. It may be tempting to save some bags, but you’ll only need to deal with leaking bags of milk once to learn this lesson.

Milk storage bags are single use and absolutely should not be reused.

If you cannot bear the thought of being so wasteful, then breast milk storage trays (Amazon | buybuybaby) are the best choice for long term freezing of breast milk.

Each slot in the tray holds 1 oz. of breast milk. Pour your freshly expressed milk into the slots and put the tray into the freezer.

Once the milk is frozen into ice cubes, pop them into a ziploc bag and label the bag with the date. Do not keep the milk cubes in the tray for a long time as the milk will pick up off flavors from your freezer.

When you’re ready to thaw the milk, just pop one or two ice cubes into a bottle and warm it up. I think the milk ice cube trays are even easier to use than storage bags since you don’t have to worry about thawing them first before you can fit the frozen milk into a bottle.

The milk trays will have to be washed every time you’re done using them, so that’s one disadvantage if you hate doing dishes.

No matter how you plan to store your breast milk, the one thing to always remember is “first in, first out”. Always use up the oldest milk first and markers and sticky notes are your friends.

If you are not good at organizing, then you can use bottle organizers or storage bag organizers which will automatically line up the containers in the right order for you.

How do I prevent freezer burn or weird rancid flavors from ruining my breast milk?

Babies are fussy eaters when it comes to breast milk and they will refuse to feed if the milk tastes odd. For safety and for your sanity, any milk that smells bad should be thrown out.

The best way to keep your breast milk from developing off flavors is to:

  • make sure the storage container is sealed tightly
  • make sure you keep the milk in the coldest part of the freezer where there are no temperature fluctuations
  • make sure you use up and renew your frozen supply within 6 months

What if I’ve done all that and my thawed breast milk still smells funny?

Congratulations! jk. You might be one of the unfortunate women who naturally produces high levels of lipase in her breast milk.

The off flavors in breast milk are caused by the fat portion going bad. Lipase is the naturally occurring enzyme that breaks down fats. Breast milk with high lipase levels will always smell rancid when frozen.

The only way around this is to bring the freshly expressed milk to a simmer before you put it into storage. Let the hot milk cool down to room temperature before you freeze it.

While heating the milk will denature some of the proteins in the milk, the remaining nutrition in your breast milk will still be better than what formula can provide your baby.

Is it normal for my breast milk to separate and look watery when it’s thawed?

Yes. Frozen milk will separate into a water and cream portion. The cream will float to the top (or float as chunks). This is perfectly normal. Warm the milk and then give it all a swirl to mix everything up again before feeding.

What color is breast milk? Is it normal for breast milk to change colors?

Yes. Breast milk will have different colors depending on what foods you have been eating and sometimes what medications you’ve been taking. Light yellow, reddish brown, green, or even slightly blue breast milk is normal. You should only worry if your milk smells bad.

Can I mix expressed milk with frozen milk or milk pumped on different days?

Yes. As long as you remember that the milk can only be kept as long as the oldest milk is good. So if you add freshly expressed milk to milk that’s been in the fridge for 3 days, then you should use up the mixed milk in the next 5 days.

You can add frozen or thawed breast milk to freshly pumped milk. Bring the bottle up to body temperature before you feed it to your baby.

Can I refrigerate or refreeze thawed milk?

Thawed breast milk (that hasn’t been kept out at room temperature for more than a few hours) can be placed back in the refrigerator. You will want to use up that milk within the next day. Dump out any milk after 24 hours.

Thawed milk should not be refrozen. The thawing/freezing process not only destroys nutrients, but it also affects flavor, mouth feel, and there’s potential bacterial growth.

How can I thaw breast milk quickly?

For milk that you are going to use right away, the fastest way to thaw frozen or refrigerated breast milk is to use a bottle warmer (Amazon | buybuybaby). If you do not have a bottle warmer, then you should heat up the milk in a pot of hot, but not boiling, water for a couple of minutes. Swirl the milk to eliminate any hot spots and test the temperature on the inside of your wrist or elbow before you feed it to your baby.

If you’re not in that much of a hurry, you can slowly bring frozen breast milk to room temperature by placing it under running cold tap water.

You should transfer frozen breast milk from the freezer to your refrigerator about 12-18 hours before you need it. This slow warming is the best way to preserve nutrients in the milk and to avoid any problems with bacteria.

Never use a microwave to reheat breast milk or to heat up a bottle. It’s faster than using a warmer or a pot of hot water, but it’s easy for a bottle to heat unevenly with cold spots and boiling hot spots that can burn your baby’s mouth.

How much breast milk should I thaw?

It’s best to thaw only as much as you need. This can be as much milk as you’ll need in the next day, or only the 1 oz-2 oz you’ll need for a feeding. Do not try to save time by thawing a couple days worth of breast milk. As you cannot refreeze thawed breast milk, you can end up wasting a lot of milk if you estimate wrong.


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