How Many Times Can You Reheat Breast Milk
Parenting Toddler Safety

How Many Times Can You Reheat Breast Milk

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Are you concerned abot how many time can you reheat breast milk?

Thanks to the ever-advancing technology, your little one can still have your breast milk even when you’re not able to breastfeed.

You’re able to store your milk and give it to your little angel at a later date.

Given that a baby has a developing immune system, parents need to know how to keep the milk safe and healthy for the baby.

This includes the pumping process, heating, and even storing it. Proper guidelines should be followed to avoid feeding them contaminated breast milk.

One of the biggest issues is whether or not breast milk should be reheated and, if it can, how many times.

Other questions you may have include how it should or should not be heated and even how to store it.

Here we have detailed yet easy-to-understand guidelines for all the questions you have concerning pumped breast milk.

So, let’s take a closer look at how many times can you reheat breast milk?

How Many Times Can You Reheat Breast Milk?

You always want to give your baby nothing but the best as a parent.

When the babies are about four weeks old, most of them have usually overcome nipple confusion from taking a bottle of breastmilk.

At this point, too, most mothers begin to think about pumping.

Pumping breast milk has a myriad of benefits, such as stimulating the production of more milk, getting some milk to feed to your baby if you are uncomfortable breastfeeding in public, or leaving breast milk to someone else to feed your baby. 

You can only reheat breast milk once, as doing so multiple times allows bacteria to thrive and destroys the nutrients inside of the milk.

If you’re worried about wasting milk, then it may be the best idea to warm up smaller amounts to prevent this.

Here we’re going to look at how breast milk should be warmed up, how long it can sit out, and the other dangers associated with it that you should be aware of.

1. Thawing Frozen Breast Milk

After you have collected the breast milk, sometimes the need arises to freeze it. Maybe you will not be available to breastfeed for quite some time.

Many caregivers do not thaw milk according to the safety guidelines.

This causes it to lose nutrients, and worse, it is more likely to spoil. The last thing you want to do is feed the baby with spoilt milk.

For this reason, following the guidelines is of the utmost importance. First, label the milk containers or bags with a date.

This will ensure that you use the milk in the oldest container first. Defrost the milk by putting it in the refrigerator.

This process takes up to 12 hours, so planning is paramount.

If you need it more urgently, put it in a bowl with warm water or simply hold the bottle under a tap with warm running water.

The water should be warm, not hot, and the temperature should be increased gradually.

It is also imperative to note that a microwave should not be used to defrost the milk.

While it may seem faster and much more manageable, it destroys the healthy nutrients in the milk and sometimes heats the milk unevenly, resulting in some hot spots which may burn the baby’s mouth.

Once the milk is defrosted, and in liquid form, it is safe to warm and give to the baby.

The milk should be used within 24 hours, and one should not refreeze the leftovers whatsoever.

2. Letting Breast Milk Sit Out

If you’ve been wondering how many times can you reheat breast milk then you’re probably also wondering how long you can leave it out.

Putting milk in the fridge or freezer makes it last longer as it slows bacterial growth.

The exact amount of time you can leave it out will depend on many factors, such as temperature.

If you are in an area or room where the temperature is quite high, the milk may take a much shorter time to spoil without refrigeration.

If the milk is freshly expressed, it is vital to put it in the fridge as it goes bad in about four hours.

If the milk was previously in the fridge or has just been thawed, it can only sit for a maximum of two hours.

At this point, it is vital to note that you should never refreeze breast milk that was frozen and thawed.

3. Combining Fresh, Refrigerated, Thawed and Frozen Breast Milk 

Sometimes it is not possible to express enough milk in a single sitting, which leaves you wondering if you should mix the fresh one with the already refrigerated one in the same container.

Under some circumstances, this is perfectly possible.

First, if the milk is collected at different times but on the same day, it is safe to add it up into the same bottle.

Before adding them up together, put the fresh milk in the fridge for about 30 minutes.

However, if you collect them on different days, it is unsafe to combine them.

Secondly, it is imperative to consider the health of your little one. Combining the milk should only be done for a healthy full-term baby.

If the baby is premature or has an immune system that is compromised, the storage bottle, once locked and stored in the fridge, should not be reopened until the baby is feeding.

Adding freshly expressed milk to defrosted milk is okay if they have the same temperature.

However, it is imperative to note that freshly extracted milk is more beneficial to the baby than thawed milk.

It is, therefore, ideal for making sure that the baby takes every drop of the fresh one wherever opportunity allows.

4. Safety Measures and Dangers Associated With Expressed Breast Milk

Other than the storage, there are other factors that may cause the milk to go bad.

One of the most common is the cleanliness of the equipment used to extract the milk.

This equipment includes the storage container and the pump. Before pumping the milk, washing your hands is vital as dirty hands may increase the number of bacteria in the milk.

If the milk has just been expressed, it has more power to fight bacteria than milk in the refrigerator or the freezer.

The longer the milk is frozen, the lesser the anti-bacteria it will possess.

Another critical factor to consider before reheating breast milk is your baby’s health.

If the little one is unwell, it is better to feed them on milk that has not been previously heated or cooled.

This is because reheating reduces the anti-bacterial properties in the milk.

Compared to formula, breast milk is safe to reheat. Bacteria tend to grow faster in formula than in breast milk.

While this is true, it doesn’t mean that you should be too relaxed about reusing breast milk. If you’re unsure, it’s always the best idea to take a cautious approach.

An essential tip in heating and reheating the milk is knowing how much your baby takes in a single feeding.

This will help reduce the amount of warmed unused milk.

This is difficult to know but if you have a bottle warmer then it makes the whole process easier and you won’t feel frustrated at reheating some more milk if your child is still hungry.

As we’ve mentioned, never heat it up in a microwave as this will warm those precious nutrients.

Another negative aspect of microwaves is hot spots as the heating is often uneven.

While that’s true, this can be overcome by shaking or stirring the bottle.

It’s important to bear this in mind if you find yourself in a situation whereby you have no other means of heating the bottle.


Just because the breast milk has been stored in the refrigerator or in the freezer, it does not mean that it can stay there for as long as you may need it to.

Actually, it can only last eight days in the fridge, after which it should not be fed to the baby.

If it is in the freezer, it can last up to six months, while if it is left to sit at room temperature, it lasts about 5 hours before it goes bad.

Burning the baby’s mouth when feeding them is not uncommon.

To avoid this, you should always check the temperature of the milk before feeding the baby.

Feeling it with your palm is tricky and misleading. Remember, the baby’s mouth is still very gentle, and what may feel just warm for you may be too hot for the baby.

After heating the milk, gently swirl the container to ensure the temperature is even.

If you do not have to have a thermometer, simply squirt a few drops on your wrist on the inside. The milk should feel warm but not hot.

By now you should know how many times you can reheat breast milk.

No matter how strictly you have followed the guidelines to ensure that the milk is contaminated, never reheat it more than once as the risk to your baby is too high.

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Frequently Asked Questions

Can I warm up breast milk and put it back in the fridge?

If the baby does not finish the warmed-up milk in the bottle, it should be thrown away unless the rest of it is consumed quickly.

It should not be stored in the fridge for future use as it has a higher chance of getting contaminated.

If you want to use more of the breast milk, then it should be left on the side and used within four hours.

If you put it back in the fridge then you may have to reheat it again, which is something you should never do.

How many times can you heat up baby milk?

While you can reheat the baby milk, this can only be done once. This is because, in reheating, all the nutrients and good bacteria in the milk are destroyed, and bacteria quickly multiply.

If it is the same milk in the same bottle that the baby was feeding with, it is safe to reheat it within four hours.

This can be disheartening with breastmilk as it feels like you have wasted your time and energy.

While knowing exactly how much your baby will drink each time is near impossible, it’s best to be cautious about the amount that you heat up to avoid wastage.

Can you reuse breast milk that has been warmed?

The simple answer is no. Breast milk should only be reheated once, after which nutrients are destroyed.

The best thing to do with leftover warmed milk is to throw it away within four hours if it is sitting at room temperature.

If the baby has already begun taking the milk in the bottle, it is unsafe to put it back in the fridge as it is likely to get contaminated by the bacteria in the baby’s mouth.

That bacteria can quickly turn bad and become harmful if it then goes back into the baby’s mouth.




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Iesha Mulla

Iesha is a loving mother of 2 beautiful children. She's an active parent who enjoys indoor and outdoor adventures with her family. Her mission is to share practical and realistic parenting advice to help the parenting community becoming stronger.

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