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The latest guidance from the United States Centre for Disease Control ( CDC ) and the Academy of Breastfeeding Medicine, is that breastmilk that has been thawed to room temperature after previously being frozen must be used within 2 hours. If the milk is defrosted in a refrigerator so that it was never brought to room temperature – you should use it within 24 hours. Do not re-freeze breast milk that has been thawed.


Moms everywhere are always multitasking. There are a thousand things to do for the little one, so finding time to pump can be difficult. Because of this, most of us pump and store milk so that we have supply handy when baby needs it – regardless of what may be going on with mama at the time. Getting that handy supply often means keeping a store of frozen breast milk within reach so that it can be warmed as needed. Whether its for work, long haul trips or just allowing mama some down time, planning and managing breast milk storage is a big part of the life of a breastfeeding mama.


In general, you will either hand express the breast milk or use a breast pump to get your breast milk into a feeding bottle or into storage bags for future use. Getting storage right is important. But. We will not spend a lot of time on storage best practice in this post. Our back-to-work guide has a section on storage do’s and don’ts, so it’s a great starting point and is worth a read even if only as a refresher.


Read more: Breastfeeding and Traveling Tips

In this post we tackle the following questions :

  • How long can you leave breastmilk out after warming it up?
  • How long is a breast milk bottle good for after warming?
  • What are some breast milk storage guidelines?
  • How long will a formula last at room temperature?
  • How long is warm breast milk good for?
  • What can expired breastmilk be used for?

In today’s article, we will address these questions and more and also provide helpful tips; starting with a quick mail from a distressed nursing mother.

Hello BreastFeedingConfidential

I just started back at the office after my maternity leave and as expected, the demands at work means I don’t always have enough time to breastfeed my baby on demand. I have planned my pumping sessions so that I always have a fridge, or freezer stash that’s available for on-demand use.

Today I read a sad story about a child that got sick after feeding from a freezer stash a day after it was warmed. I am now just a bit concerned about this, and would like to get your view on how to manage reheating milk for feedings.

I think I have a good process where I mark each milk bag with a date and time and I’m careful to use the first-in-first-out method. Is there anything else I need to be thinking about?

I am not usually a worrier, but I’m a first time, single mom, and I really want to get things right. Any advice you can share would be really great. I look forward to hearing from you.

Yours Truly,




There’s a lot to unpack in that message, but for the purposes of this post, we will focus on just the mechanics of safe handling of preserved milk.

  • How long is warmed breast milk supposed to last? How long can we leave the frozen milk out after warming it up? Is it better to defrost previously frozen milk in the refrigerator or by heating it up directly?

This is actually one of the more straightforward aspects of milk handling.

The whole point of warming up breast milk is to get it from cold, to room temperature. Room temperature means 25 degrees Celsius or 77 degrees Fahrenheit. Room temperature is barely warm.

Some babies may prefer milk to be a little warmer since breast milk is warm when babies nurse.


In course of warming up your baby’s cold breastmilk, here are a few guidelines to follow.

Air-tight is Alright

Whether the milk is in a bottle or a milk bag, its usually a good idea to check that the container is properly sealed.

You likely checked this before freezing or refrigerating the milk in the first place, but its worth another check before the milk is brought to room temperature. Its best to completely seal off the baby’s feeding bottle to avoid contamination from the environment and also prevent water penetration. If your pumped or expressed breast milk is in a storage bag then it’s best to repeatedly make sure that the zip lock is in place.

A baby's feeding bottle that is being properly sealed

Hot is too hot

This particular warming guideline is vital to avoid the breakdown of the nutrients contained in human milk, as well as prevent chances that baby might be scalded, especially since ‘warm’ to you is a notch hotter for them.

Breastfeeding moms should try to avoid making the mistake of heating the baby’s feeding bottle or storage bags directly in hot water or even in the microwave.

In addition to increasing the risk of scalding, heating the milk causes more fat loss than accelerates break down of the milk. The end result is that the milk is less nourishing for baby.

The safest method of warming up a bottle rotates around either using a bottle warmer or by placing some warm water in a bowl or mug and then inserting the bottle or storage bags into it while making sure that the lid area is not covered by water.

Frozen milk can also be thawed by holding it under a running tap or lukewarm water for a couple of minutes till it gets to an optimum room temperature since frozen milk should not be thawed at room temperature. But if the breast milk defrosts first, then, you can slightly heat the expressed milk and use it immediately.

Based on medical advice, it is important to note that leaving the milk at room temperature for more than 4 hours or placing the milk in the fridge or in the refrigerator for more than 24 hours is unhygienic.

The warming of a baby's bottle in a bowl of warm water

Milk Mix

After allowing the feeding bottle or the storage bag to sit in the bowl of water for 30-60 seconds, it should be retrieved and intermittently swirled or mixed to allow the even distribution of heat as well as the balanced spread-out of the fattish breast milk to prevent hot spots.

It is also important to note that the omission of this guideline might bring about an uneven distribution of heat which might lead to an ouch episode with your baby.

Traveling baby

Temp. Test

This rule portrays the importance of testing out the temperature of the expressed breast milk by popping a few drops from the bottle or storage bags onto your wrist or the back of your hands since your skin tolerance cannot be compared to that of your baby.

Now, that your baby’s warm bottle is ready. How long can it be good for before being discarded?


Based on the report from experiential research as well as the general guidelines from the Academy of Breastfeeding Medicine, it could be said that the potent life cycle of a pumped or expressed breast milk is invariably mapped at 2 hours after warming. This expiration time of 2 hours is due to the scientific observation that a warm environment is a sweet spot for survival of numerous bacteria.

A cute baby reaching out for a feeding bottle

However, to avoid accidentally feeding your newborn baby; with expired breast milk, here are 3 clear guidelines for any warmed or thawed breast milk that may be best sent anywhere but baby’s tummy.


Some child care guidelines for discovering that breast milk is bad include:

Death Smell

The first telltale sign of expired breast milk is the dangerous odor it will emit. This sign enjoys announcing its presence with a foul smell that may be bad enough to force you a gag reflex.

There’s no missing it.

Again, to avoid this you want to make sure that warmed breast milk at room temperature is used within 2 hours while the cold milk in the fridge should be used within 24 hours. But, once you notice the smell. Do not feed it to baby.

No Swirl

The second clue of expired breast milk is its tendency to chunk up and not re-mix again. Whenever freshly pumped or expressed breast milk is left undisturbed, the fatty and less fatty constituents would separate into upper and lower regions, only to swirl or mix when touched or slightly shaken; unlike the expired breast milk.

Image showing two expired breast milk in storage bag

Musty Taste

The last indication of spoilt breast milk is the sour taste it would leave behind which is a direct contrast to its natural taste.

A little more on storage …

At home, freshly expressed breastmilk can be stored in the back of the refrigerator for 4 days, in a standard freezer for 4 months, and in a deep freezer for 8 months.

When you are on the road, milk can be stored with the use of an insulated cooler or with the use of ice packs. The ice packs should be placed on the breastmilk which is to be kept in a human milk storage container. The insulated cooler should be properly sealed to prevent the escape of gas and the spoilage of the freshly expressed milk.

When thawed, the previously frozen breastmilk should be used within 24 hours, but when warmed, breastmilk should be used within 2 hours.

If the breastmilk shows signs of spoilage, then the milk within should be discarded and then thoroughly cleaned with soap and water. Close attention should be paid to the breast pump, bottle, and storage bag which is the equipment used for pumping and storing breastmilk.

Sometimes, especially after the rigor of pumping and storing breastmilk process, some nursing mothers may get sentimental when it comes to dumping out leftover breast milk that has been sitting out longer than the stipulated time.

We get it. And clearly its not ideal.

But we cannot overemphasize the fact that a baby’s health is priority number one. Nothing beats, protecting your precious little one by giving them the safest and best nutrition they deserve in the form of high quality breast milk. So, “If you are in doubt, throw it out!”

So, once the 2 hours or 24 hours time frame is up, all previously warmed breast milk, thawed breast milk, and leftover milk must not be consumed.

Clearly, the last thing anyone wants is to put themselves or their little one at risk. So what do you do if you have a stash of breastmilk that’s crossed the line? Well, you still have readily available options.


A baby receiving a breast milk bath

There are ways to use leftover breast milk without discarding it. Uses range from breast milk baths, use in lotion, cremes or soap.

Breastmilk contains vital nutrition that many people believe it could serve as a body refresher, and can be helpful in the treatment for many kinds of skin allergies or infections – think rashes, bites, eczema, etc.

We won’t go into too much detail on this in this post, but remember that even if it is expired and cannot be fed to a baby, breastmilk may not need to be thrown out.