How To Warm Breast Milk – 3 Safe Step-By-Step Ways

How to warm breast milk and storage guidelines.

How To Warm Breast Milk

For any mom that wants to pump and give her baby the milk, it’s extremely important to know how to warm breast milk. Some ways of heating breast milk are better than others. 

And some ways of heating breast milk can actually harm your baby. 

I don’t recommend using a microwave at all, but if you insist this guide will give you the steps to do it in the safest way possible

How should you warm up breast milk.


Steps To Warm Breast Milk

The recommended way to warm breast milk is in a hot water bath. Here are the steps to take: 

  1. Fill a bowl with water and microwave it until it’s hot but not boiling. 
    • Alternatively, you could heat water in a kettle until it’s hot but not boiling, and then pour it into a bowl. 
  2. In a sealed container, place the breast milk into the warm water. 
    • The amount of time it takes to warm depends on the amount of milk. 2 ounces will take about 3 minutes. 
  3. Pull the milk out and feel the sealed container. When it is about body temperature, it is warmed adequately. 
  4. Wash your hands and pour the breast milk into a bottle to give your baby.  

If you want to heat 2 ounces of refrigerated breast milk, it would take approximately 3 minutes for the bottle to be adequately warmed in a water bath of warm water. If there’s more milk in the bottle, it may take a bit longer. 

A hot water bath is efficient because it has strong thermal mixing, meaning that there are no “hotspots” in the milk, and it’s heated throughout.

In contrast, a microwave may burn your baby’s mouth because it doesn’t heat evenly. Some spots get extremely hot, which can not only cause burns, but those “hotspots” cause denaturing of enzymes and compromised milk quality.

 Even if you test it, there may be hot areas within the volume of milk that start to break down the nutritional parts of the milk.

Warming Breast Milk With A Baby Bottle Warmer

Another great option for warming breast milk is a baby bottle warmer. They are small containers that can be filled with water that the bottle will then be placed in. 

Follow the manufacturers instructions for the amount of water according to the volume of breast milk. Then:

  1. Wash your hands.
  2. Pour in the recommended amount of water.
  3. Put the breast milk into the baby bottle you’ll use.
  4. Place the baby bottle of milk into the bottle warmer.
  5. Turn the baby bottle warmer on.
  6. Wait for the length of time as instructed by the warmer manufacturer.
  7. Test the temperature of breast milk.
  8. Feed your baby.

A baby bottle warmer works in a similar way to a warm water bath, it just heats the water for you while the bottle is inside of it. 

Be sure when giving your baby previously expressed milk that you follow breast milk storage guidelines. 

Breast milk storage guidelines for moms.

Breast Milk Storage Guidelines


The CDC has put out guidance for breast milk storage. The breast milk storage guidlines are above, and I will go over them in detail here. 

For breast milk that has been freshly expressed, it can sit out for 4 hours before feeding it to your baby. Some people say it is good for 6 hours, but since the CDC recommends 4 that’s what I’d suggest. 

If you refrigerate your breast milk immediately after you pump, it will be good for 4 days. Similarly to freshly expressed breast milk, if you take refrigerated breast milk and set it out, use it within 4 hours. 

If you freeze your freshly expressed breast milk, it will be the best when used within 6 months. But you will be able to use it over the next 12 months. Additionally, you can freeze fresh milk within 4 hours of sitting out, or refrigerated milk within 4 days. 

Milk that’s been previously frozen has different guidelines. It can sit out for a maximum of 2 hours before giving it to your baby, and can only be refrigerated for 1 day. 

Never refreeze human milk after thawing it. 

When you baby drinks from a bottle, it must be used within 2 hours. Their mouth contaminates the breast milk and it needs to either be used within 2 hours or discarded. Even if you put it in the fridge, bacteria could grow. 

Babies have fragile immune systems at first so follow the guidelines a closely as possible for your little one’s safety. 

How to warm and store breast milk.

How Long Does Breast Milk Last In The Fridge?

Freshly expressed breast milk will last for 4 days in he refrigerator. If the breast milk was previously frozen, it will last 1 day (up to 24 hours) in the fridge. 

But, if your baby has contaminated the milk (by drinking from the bottle but not finishing it), the milk is only good for the next 2 hours and then should be discarded. 

How Long Does Breast Milk Last After Warming?

After warming refrigerated breast milk, it’s good for the next 4 hours. If your baby drinks from the bottle though, use the milk within the next 2 hours because bacteria is introduced from your baby’s mouth. 

Frozen breast milk will last 1-2 hours on the counter after it’s warmed, so make sure to either use it or discard it. But if you place frozen breast milk into the fridge, it will last for 1 day. 

How Long Can Breast Milk Stay In The Freezer?

Breast milk is best if it’s used within 6 months of freezing it. It is acceptable to store frozen breast milk for one year, but after that it should be discarded. 

Breast milk shouldn’t be stored in the freezer door because the temperature fluctuates. Keep it on an internal shelf or in a chest freezer for more stable temperatures. 

If breast milk thaws, don’t refreeze it. 

How to microwave breast milk.

Microwaving Breast Milk

I’m sure you’ve heard that microwaving breast milk ruins it. Doctors tell you not to microwave your breast milk, grandma tells you not to… But does the microwave really ruin it?

Can you microwave breast milk?

You CAN… But it does change the contents in the milk. Overall, it’s better to never microwave breast milk. This is due to the loss of nutrients when heated, but also to avoid burning your baby’s mouth. 

My professional advice is to not microwave your breast milk– but I know that when you have a screaming baby, you want the fastest possible way to make your breast milk warm. 

I will give you the information on how the microwave affects breast milk, and then tell you that if you still decide to microwave it, you should follow specific steps.

Here’s the research: 

Heating breast milk can denature lipase, the enzyme responsible for breaking down fat. When this happens, it’s more difficult for a baby to absorb the fat in the milk, because they don’t have the help of lipase to break it down. In fact, heating it too much can reduce fat absorption by as much as 30 percent! This is important because our babies need fat; it makes up almost half of the calories they get from breast milk. With all the growing they do in the early days, those calories are vital.

Another study showed that milk quality is compromised at hotter temperatures. During the pasteurization process of human milk, researchers noted that immune properties and other nutrients (sIgA, lactoferin, lysozyme, white blood cells, and probiotics) were destroyed. The good news is the denaturing of lipase typically only occurs at temperatures over 40 degrees Celsius (around 104 Fahrenheit). That’s roughly body temperature, or what most people would describe as “lukewarm”. As long as temperatures are not significantly higher than that, the nutritional value of human milk is sustained.

How to heat breast milk in the microwave (if you insist):

I totally get it. You have pumped milk that needs to be given to your baby (whether it’s a babysitter, your husband, yourself). When your baby is so hungry they’re screaming their head off, 3 minutes feels like an eternity to wait for the milk to get warm in a bath. So if you decide that the time benefit outweighs the cost of nutrition and burn risk, here’s what you do:

1. Only heat it for 10 seconds at a time.

This ensures that you don’t overheat the milk because if you test the temperature every 10 seconds, you won’t overdo it. Every 10 seconds, pull the bottle out and see what the temperature is.

I will note that it could take some time for the milk to warm, and it may be a better option to just use a warm water bath… just saying!

2. Swirl it every 10 seconds (after you remove it from the microwave).

It doesn’t completely eliminate the “hotspots”, but if you swirl the milk it will have a more even heating temperature. The hotter areas within the milk will be dispersed into the cooler areas. This also prevents the “hotspots” from becoming too hot. 

It’s probably best not to shake the milk, which may cause bubbles. Some babies don’t do well with bubbly milk- they could become more colicky.

3. Make sure you swirl the milk WELL and TEST it before feeding.

This is a must. I would give it no less than 10 swirls around, just to make sure that the “hotspots” are gone. Then, swirl it 10 times in the opposite direction. Test the milk on an area of your own skin that can easily feel heat like the soft skin of your inner wrist.

 If it’s too hot, DO NOT FEED it to your baby

You could burn them. Remember: you only want it to be lukewarm, about body temperature. That’s the temperature of breast milk as it comes from your body, and that’s what is best for your baby.

How to Microwave Breast Milk From The Freezer

When pulling breast milk from the freezer, follow these steps to thaw it: 

  1. Fill a large bowl with water. 
  2. Microwave the bowl of water on high for 2-3 minutes or until it is warm but not boiling. 
  3. Place the frozen bag of breast milk in the water for 2-3 minutes or until it thaws and reaches a lukewarm temperature. 
  4. Pour the breast milk into a bottle. 
  5. Swirl the breast milk to incorporate any fat and evenly distribute the temperature. 

Again, it is never recommended to place breast milk directly in the microwave to heat it. If you feel you absolutely cannot wait for the milk to thaw in the water bath, follow the steps above to microwave the breast milk from the freezer. 

Please be safe, heat the breast milk in intervals and test it before giving it to your baby. The last thing you want to do is burn your baby;s throat and mouth. 

Although it takes time, the best way to warm breast milk is to set it in a warm water bath. That will keep your baby safe and the breast milk nutrients intact. 

How To Warm Breast Milk: Conclusion

In conclusion, the best way to warm breast milk is to place it in a warm water bath. In 3 minutes, the milk will be body temperature and safe for your baby to drink.
Always follow breast milk storage guidelines and don’t give your baby milk that’s been sitting out for too long. 

Many breastfeeding moms breast pump, and knowing how to warm breast milk afterwards is extremely important! 

Please don’t hesitate to reach out to me if you have any questions!

Kealy Hawk lactation consultant
Kealy Hawk, BSN, RN, CLC

Kealy is a Registered Nurse, Lactation Counselor, and most importantly a mommy! Her own baby feeding struggles gave her a passion to help moms throughout their feeding journey. She specializes in breastfeeding support and evidence-based formula recommendations. To talk with Kealy or take one of her breastfeeding or formula classes, visit

Breast milk storage guidelines and how to warm it up for your baby.
How to warm up breast milk safely.
How to warm and heat up breast milk.

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