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How to Warm Up Breast Milk

Medically Reviewed by Michelle Roth, BA, IBCLC
Updated
Learn about the proper storage and preparation methods of breast milk.

Can breast milk be heated after it’s been stored in the fridge or freezer? What’s the best way to prepare stored breast milk?

If you choose to pump your breast milk, you’ve probably asked these questions. Many women choose to pump and store their breast milk because they’re looking for greater flexibility in their feeding schedule.

However, that comes with some technical requirements, like keeping your breast milk cool while it’s stored, and heating it properly to ensure it’s safe for your baby.

In this article, we’ll discuss everything you need to know about how to warm up breast milk.


How Should I Store Breast Milk?

If you choose to pump your breast milk, it needs to be stored in a cold place until you’re ready to use it again. The methods you use to store your breast milk should be determined by when you plan to use it next.

Breast Milk Containers

There are many containers specifically created to store breast milk. They include:

You can even purchase entire kits that contain a breast milk cooler, a breast pump, and storage containers. Avoid using regular plastic bags, as they can burst when frozen and the plastic may leech into the breast milk.

Best Temperature To Store Breast Milk

It’s important to store your breast milk at the correct temperature to prevent bacteria from growing, especially if you’re storing a half-used bottle that’s been exposed to saliva.

The U.S. Centers for Disease Control and Prevention provides these helpful guidelines to ensure safe storage (1):

  • Fresh breast milk: Freshly pumped breast milk can be stored in a 40°F refrigerator for up to 4 days or in a 0°F freezer for up to six months.
  • Thawed breast milk: Thawed breast milk can be placed back in the refrigerator for up to 1 day. It should never be refrozen and reused.
  • Unfinished bottle: You need to reuse breast milk from a bottle your baby has fed from within 2 hours of the feeding. It can be stored right on the counter or in the fridge. After 2 hours, dispose of it. The saliva will start breaking down the enzymes in the milk and bacteria can grow.

You may want to get a storage system that allows you to keep track of how long breast milk has been in your freezer or fridge. You can also develop your own using post-its, chalk markers, or whatever you find easiest.Breastmilk Storage Guidelines Chart

Why Heat Breast Milk?

The fact is, you don’t need to heat breast milk. Your breast milk does not need to reach a certain temperature after it’s been thawed to be usable. As long as it has reached a liquid state, without any ice crystals, it’s safe for your baby to ingest.

However, many babies prefer warm breast milk. Heating the breast milk can take off the cold edge, making for a more comfortable feeding experience. Warm breast milk can also help soothe and calm babies during feedings.

How Do I Heat Breast Milk?

Heating breast milk is simple. Just follow these three steps:

  • Thaw: Thaw your breast milk in the fridge overnight. It should reach a fully liquid state. Do not thaw frozen breast milk at room temperature.
  • Warm: Place the thawed breast milk into a bowl of warm water for 20 minutes.
  • Swirl: Swirl the milk inside of the bottle to evenly distribute the heat and reconstitute it.
If you’re in a hurry and your milk is frozen in bags, you can thaw and warm the milk by holding the bag under running warm water. You can use your fingers to break up the ice crystals, speeding the process along.
Headshot of Michelle Roth, BA, IBCLC

Editor's Note:

Michelle Roth, BA, IBCLC

The thing you need to be most careful of is overheating. If breast milk becomes too hot, it not only loses some of its beneficial nutrients, but can burn your baby. The bottle, especially if it’s glass, can also overheat and burn your baby’s skin when touched.

Pro Tip

Never heat breast milk in the microwave. Microwaves heat unevenly, which could cause hot spots. You will also have a hard time ensuring your breast milk has not become too hot.

Heating Breast Milk On The Go

Unless you plan on never leaving the house with your baby, there will like be times when you need to feed on-the-go without the comforts of home. While some mothers choose to breastfeed in public, others choose to bring bottles of breast milk with them.

Here are a few ideas on how to keep the breast milk flowing, no matter where you’re going.

1. Bring Thawed Bottles

Thawed breast milk can be kept at room temperature for two hours. If your outing is short, just store the thawed bottles in your favorite diaper bag.

2. Bring a Cooler

Product Image of the Medela Breast Milk Cooler and Transport Set, 5 ounce Bottles with Lids,...

If you plan to be out for an extended period of time, consider a more long-lasting storage solution.

If your baby will drink cold breast milk, carry the bottles in a cooler such as this one. It will keep your breast milk safe for up to twelve hours.

3. Bring a Travel Warmer

Product Image of the Tommee Tippee Closer to Nature Portable Travel Baby Bottle Warmer - Multi...

If your baby prefers warmed breast milk, keep the bottles in the cooler but use a travel bottle warmer to heat it up. You can also run the bottle under hot water in a bathroom or ask a restaurant waiter for a glass of hot water.

Avoid keeping breast milk in a hot car and make sure to keep track of how long bottles have been sitting out at room temperature to avoid spoiling. Always check the temperature before giving to your baby.

Checking Breast Milk Temperature

Product Image of the Baby Bottle Thermometer, Automatic Milk Temperature Thermometer Monitor with...

The easiest way to test the temperature of breast milk is to place a few drops on the inside of your wrist. It should be slightly warm, but not hot. If you believe it’s too hot, imagine the effect on your baby’s sensitive skin!

You can also purchase a small temperature checker designed with bottles in mind. All you have to do is place the bottle on the small scale and the device will tell you the temperature of your bottle.

The ideal temperature for breast milk is approximately 98.6°F, just around the average body temperature.

Don’t put your finger in the breast milk or place the bottle to your lips — this will increase the risk of passing germs on to your baby.

Can You Over Heat Breast Milk?

The major concern with overheating breast milk is burning your baby’s sensitive mouth and skin as they try to drink the milk or touch the hot bottle.

Overheating also damages the breast milk, destroying many of the important nutrients your baby needs (2).

If you accidentally overheat a bottle of breast milk, you can cool it down and it will be safe for your baby to drink. However, you want to make sure the breast milk is used within two hours.

Does Heating Change Breast Milk?

Your breast milk may look slightly different after you store it and when you heat it.

Once milk is refrigerated or frozen, it may separate. The fat in the milk travels to the top while the liquid sinks to the bottom. Simply swirl the bottle once it’s warmed to mix the solids back in.

After heating, it’s normal for your breast milk to change color. It may take on a blue, yellow, or even brown hue (3). This discoloration is not generally a sign something is wrong with your breast milk and is still safe for your baby to drink.

When Breast Milk Goes Bad

There are times when a bottle may have been left out too long, or that thawed portion of breast milk in the fridge doesn’t seem right. In these situations, it’s key to remember that breast milk can go bad.

There are a few key identifiers to spotting spoiled breast milk.

1. Curdling

Just as with cow milk, the most obvious sign of spoiling will be a bad odor and curdling. Even though your breast milk may separate, it should easily mix back together. If it does not, it may be bad.

2. Sour Taste

If you’re concerned about your breast milk and these other signs are unclear, taste it. If it has gone bad, It will have a strong sour taste.

3. Smells Soapy

Occasionally stored breast milk will have a smell or taste that is often described as soapy. This is thought to be from excess lipase in your milk. This milk is still safe for your baby, though some babies reject the milk because of the change in taste.

If you believe this is happening with your milk, you can try scalding and quickly cooling freshly pumped milk before storing it (4). If you have previously frozen milk that your baby won’t accept, consider trying to mix it with freshly pumped milk.

There’s not any known way to get rid of the soapy smell and taste once the milk has been frozen and thawed, though some moms suggest adding vanilla extract may make it palatable.

4. Play it Safe

If you’re unsure as to whether or not breast milk has gone bad, play it safe and throw it out. Make sure to keep track of how old your breast milk is. Many freezer bags and bottles have space for you to write the date and time.

Use the breast milk with the oldest date first. Sort them in your freezer so they are right in front and ready to be taken out first.

Pro Tip

Make sure you clean and sterilize your bottles and breast pump properly. If not properly cleaned, old breast milk stuck in the bottle or pump can contaminate new breast milk (5).

Headshot of Michelle Roth, BA, IBCLC

Medically Reviewed by

Michelle Roth, BA, IBCLC

Michelle Roth, BA, IBCLC is a writer, editor, and board-certified lactation consultant for two busy pediatric practices. She is a former La Leche League Leader, Lamaze Certified Childbirth Educator, and Certified Infant Massage Instructor.

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