How Long is Breast Milk Good for After Heating?

  • By: Sandra
  • Date: August 9, 2022
  • Time to read: 9 min.

If you’ve made the decision to start expressing breast milk for your little one, it’s important to familiarise yourself with how to handle and store expressed milk.

You can certainly feed freshly expressed breast milk directly, but if you expect to pump more than your little one will eat, you need to know the best ways to store breast milk, how to heat breast milk, defrost frozen breast milk, and what to do with leftover breast milk.

Every drop of breast milk is precious, so it’s important to get yourself up to speed on human milk storage information, such as how long the breast milk will last in each condition, and the pro’s and cons of each storage condition.

You should even consider if you want to pump and express milk before your baby is born, we go through he pros and cons of pumping before birth here.

Before You Express or Handle Breast Milk

Express breast milk

Proper storage and preparation is essential to prevent waste of breast milk, so read on to find out everything you need to know before you store expressed breast milk. Here are a few basic tips before you start:

  • If you are using a shared pump kit, be sure this is properly sterilised before use; this includes the tubes and collection container, as well as wiping down the controls. Only use a closed system breast pump if you are sharing with someone else.

  • Always thoroughly wash your hands, along with storage containers. Some moms prefer to use pre sterilised storage bags. The added bonus of using plastic bags rather than containers is that they can be a lot more space efficient, particularly important if you are freezing breast milk to build a good stash

  • For full term infants, you can wash your pump parts in warm soapy water between uses. If you are expressing breast milk to donate to a human milk bank, be sure to follow their instructions for the storing and handling breast milk for disease control purposes. An electric pump might be more efficient for this purpose.

  • Whether you use a manual or electric pump, pumping can be hard work. We recommend storing in small quantities to reduce the risk of waste (which is devastating!)

  • If you experience any difficulty with expressing or require help with methods, consult with a lactation consultant who can advise. They can also advise on natural ways to increase milk supply

What is the Best Method of Storing Breast Milk?

Storing Breast Milk

The best method of human milk storage really depends on your circumstances. If you are pumping breast milk occasionally for fairly quick use, this can be stored at room temperature for up to 4-6 hours.

Your baby may like room temperature breast milk as this isn’t too far off body temperature- which is how they are used to drinking it!

You can also refrigerate freshly expressed breast milk. Refrigerated breast milk will last for up to 3-5 days. Pop the container sealed in to the back of the fridge, not in the door where temperatures fluctuate.

If you’re on the go, you can use an insulated cooler with ice packs to store your milk short term- it should be good for 24 hours.

If you intend to build up a large stock of breast milk, frozen milk can be stored for up to six months. It’s better to use plastic bags for storing breast milk in the freezer in large quantities, as these can be frozen flat to save space- breast milk bottles can fill your freezer very quickly!

Thaw frozen breast milk in the fridge to give you the most time for use; room temperature thawed breast milk is good only for around 2 hours, while fridge thawed breast milk should be good for 24 hours.

Frozen milk does lose some of the immunological and nutritional benefits compared to freshly expressed breast milk. Many infants rely on frozen breast milk, however, so more research is needed in order to optimise methods of storage and thawing.

How Long Can Expressed Breast Milk be Stored?

This depends on the method of storage, as well as how meticulous you have been with the hygiene and preparation of breast milk.

Freshly expressed milk can be stored for 4-6 hours at room temperature, 3-5 days in the fridge or up to 6 months in the freezer.

Breast Milk Storage Tips

Breast Milk Storage
  • Always date your milk, so it can be used in date rotation

  • Use good hand hygiene and thoroughly clean your pump parts and any storage containers.

  • if you are travelling, you can use an insulated cooler with ice packs to preserve your milk for up to 24 hours

  • Store milk in small quantities of 2-4 ozs in order to prevent waste.

  • If freezing milk, use bags which can be stored flat, rather than bulky containers.

  • Breast milk is best used fresh, with the next best option being refrigerated, and then frozen. Bear this in mind when choosing the storage method each time you express milk.

How to Store Breast Milk in the Fridge

If you’re storing breastmilk in the fridge, you will need to use it within 5 days. This is fine if you are an occasional pumper and just need fresh breast milk to cover you now and then.

If your baby prefers warm breast milk, you can use a bottle warmer or a bowl of warm water to ensure that you have a supply more or less ready to go, with no need to thaw.

Refrigerate expressed breast milk immediately, in a sealed storage container. Be sure to add the date of expression so that you use pumped milk in order, the oldest breast milk first.

Just as cow milk spoils, so does breast milk – so use in a date rotation and within 3-5 days. This helps to preserve nutritional value too.

Do not store breast milk in the refrigerator door, where it will be susceptible to temperature changes every time the door opens.

Store milk in quantities of 2-4 ozs, according to what your baby takes in a typical feed- once the milk has been exposed to baby’s mouth, leftover milk must be used within 2 hours.

How to Store Breast Milk in the Freezer

Breast Milk in the Freezer

If you are storing your breast milk in the freezer, the best way to do so is using disposable bottle liners or storage bags. These can be frozen flat so as not to take up all your deep freezer space!

Again, ensure to date your milk and use in date order. If your child attends day care, also add your child’s name for the benefit of your child care provider.

Freeze your breast milk in quantities of 2-4ozs- this prevents waste. It is not recommended to refreeze thawed breast milk, so you want to freeze in quantities that can be consumed within one feed.

If you plan to freeze your breast milk, remember that breast milk expands as it freezes, so in order to prevent your frozen container from breaking or bursting, be sure to leave a gap of an inch or two at the top of the bottle, and do not fill bags past the fill line.

You can check out our post about freezing breast milk to learn more.

Hot to Safely Thaw Breast Milk

Thaw Breast Milk

There are a number of ways to thaw breast milk. You can pop the bottle or sealed bag in to a bowl of lukewarm water, or thaw in the refrigerator (this can take around 12 hours so will require some forward planning).

You can also run the sealed container or bag under warm water until completely thawed. Thawing breast milk at room temperature is not recommended.

Previously frozen milk thawed in the refrigerator should be used within 24 hours, while room temperature breast milk should be used within 2 hours of thawing- it can be served room temperature.

Never refreeze thawed breast milk.

Never heat frozen breast milk in the microwave; this can lead to hot spots which may burn your baby’s mouth. It is best for breast milk to be thawed slowly, for example running under hot water.

You can use a bottle warmer to warm your thawed milk, but it should then be used within 2 hours.

Storing Breast Milk at Room Temperature

Storing Breast Milk at Room Temperature

Store expressed breast milk in a quantity your baby is likely to eat within one feed- usually between 2-4ozs. Once your baby has taken the bottle, you can only reuse breast milk leftover within 2 hours of the feed commencing.

For most babies, there will be no need to reheat room temperature breast milk, though some do prefer warm breast milk- this just depends on your baby!

Bottle warmers can be used to bring the milk back to something similar to body temperature, which your baby is used to. Do not reheat breast milk after the first heating.

Just like cows milk, human milk will spoil if your storage area is particularly warm, so be sure to use within around 4 hours of expression, and keep the milk away from direct heat sources.

Feeding Expressed Breast Milk

When feeding expressed breast milk, you want to waste as little as possible- this is why the breast milk storage tips above are crucial!

When you’ve offer the bottle, any leftovers must be used within 2 hours, and discarded after that time.

Breast milk can be offered cold, at room temperature, or gently warmed up. You can try your baby with all of the above to see which they seem to prefer.

Heating Breast Milk

Heating Breast Milk

If you do decide to heat breast milk, do make sure to heat gently, with lukewarm running water or a bottle warmer, rather than a microwave or over the stove.

This prevents hot spots which could cause burns in your baby’s mouth, and also helps to protect all of the nutritional benefits of the milk.

If you do heat expressed milk, be sure to test the temperature before giving the milk to your baby. Still have questions? Read more of our advice about how to heat breast milk.

Can Breast Milk Be Reheated?

Breast milk should not be reheated.

Once the milk has been thawed and heated, use it within 2 hours. After this time, any leftovers should be discarded.

When do I need to Throw Out Expressed Breast Milk?

If your milk has been stored for more than 4-6 hours at room temperature, 3-5 days in the refrigerator or 6 months in the freezer, it’s probably time to toss it.

Breast milk smell varies from person to person, so it’s good to get used to the normal smell of your milk so that you can be vigilant and spot spoilage in your milk. Read our blog post on how to tell if breast milk is spoiled for more advice.

You should also discard milk leftovers within 2 hours of heating and offering to your baby. Remember though, there is lots you can make with spoiled breast milk.

Breast Milk Storage, Thawing and Heating: The Bottom Line

The best method of storage for you will depend largely on the quantity of milk you intend to express. Consider how much milk you need to store and for what length of time, and make a decision from there.

Always be meticulous with hygiene and labelling your containers with the date of expression. Use expressed milk within the time frames recommended above.

If you do decide to freeze breast milk, make sure that you thaw the milk gently to protect the nutritional benefits of the milk, and to reduce the risk of burns. Freeze in small quantities, because, once thawed, breast milk cannot be reheated.

Breast milk does not necessarily need to be heated, but if your baby prefers it, do this gently and be sure to test the temperature before giving to your baby. Never heat breast milk in the microwave or over the stove, instead run under hot water.

Be sure to use expressed breast milk within the recommended time frames; within 4-6 hours at room temperature, 3-5 days in the refrigerator or 6 months in the freezer. Once defrosted or offered to baby, any leftovers must be used within 2 hours, and discarded after this time.

With all of that said…good luck in your pumping journey!