BabyFeedingHow Long Does Breast Milk Last After Warming?

How Long Does Breast Milk Last After Warming?

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Storing expressed breast milk saves time and gives you a ready supply to ensure your baby is well-fed – at any time. But how long is breast milk good for, especially after warming? We’ll answer this and more. Depending on your storage method, breast milk can last months. However, introducing it to heat cuts its lifespan significantly. Put simply, once you thaw or warm frozen breast milk, you have limited time to feed it to your infant.

How long does breast milk last after warming? Once the milk is at room temperature or warmed up, ensure that you give it within two hours and not more than that. The longer it is at room temperature or warmer, the greater risk of bacterial growth.

In comparison, freshly pumped milk can be stored at room temperature for 4 hours max according to the CDC guidelines.

It is best to thaw frozen milk in the refrigerator. If you plan on using the milk, you can place it in the refrigerator for the night.

Is it Okay to Store Breast Milk?

Yes, it is fine to store breast milk. You should have a steady supply of breastmilk in cases of emergency or if you cannot express enough for the day.

Moms can often be busy and trying to feed a child while handling other tasks can be difficult. Other practical reasons are if you put your child in daycare or your child is not feeding well. These, amongst other reasons, are why having a handy supply available is a no-brainer.

Stored breast milk serves as a contingency in situations where you are not at liberty to feed your child. Expressing and storing it requires some degree of discretion and tactfulness.

Breast milk is only safe when you handle it properly. Cleanliness is not negotiable. Wash your hands and ensure all the things you use to handle them are clean or sterilized.

Always use clean breast milk storage bags. Label them clearly and include the date of expression before storing them.

How Long Is Breast Milk Good For?

Knowing how long breast milk lasts after warming is crucial for ensuring that babies receive the nutrition they need while preventing waste and potential health risks. Therefore, you need to know how long breast milk lasts, especially after warming.

Breast milk can last up to four days when stored in the refrigerator. According to the Centre for Disease Control and Prevention breast milk storage guideline, frozen breast milk can last up to 12 months under the right conditions. However, once it has been thawed or warmed, its life span becomes pretty short. Thawed breast milk should be consumed within 24 hours, while warmed breast milk is safe for only 2-3 hours.

If not consumed within this time frame, the milk will start to breed harmful bacteria that may cause foodborne illness. Therefore, you should discard leftover breast milk immediately. According to the same guidelines, you should not refreeze breast milk that has been brought to room temperature. Experts recommend that you only dispose of what’s left.

While breast milk is most popular for its vast nutritional value, a critical constituent is bacteria. According to a recent study, the present good bacteria community aids the child’s nutrient absorption and immune system development.

Meanwhile, from the moment milk is expressed, other bacterial action and growth begin. Given that freshly expressed, thawed, or warmed breast milk is at room temperature, bacteria proliferation happens faster. While the rate is unclear, experts strongly suggest it’s best to stick to the two-hour timeframe after warming.

Some noticeable changes include a change in color, foul odor, and surface inconsistency even after shaking.

How to Warm Up Refrigerated/Frozen Breast Milk

Warming up refrigerated or frozen breast milk is a simple process, but it is vital to do it appropriately. Moreover, it is important to note that overheating breast milk can decrease its nutritional value.

Microwaving, therefore, is a NO-NO!!! It may result in uneven heating, damaging the milk’s enzymes and antibodies, thus reducing its nutritional value. The same applies to putting a milk container in a pot of boiling water.

Below are ways to warm up breast milk:

  • Room Temperature: The best and most natural way to warm breast milk is to take it out of the refrigerator and let it settle to room temperature by itself. This process should take about three to four hours. For frozen milk, you should move it from the freezer to the refrigerator compartment first before taking it out to room temperature. This can take anywhere from 8-12 hours depending on the size and ice particles. So, always plan ahead.
  • Warm Water Bath: Another way to warm refrigerated breast milk is to submerge the milk container in a bowl of warm water. The water should be warm to the touch, not boiling. This method is safe and effective, and the milk will usually warm up in 30 minutes.
  • Bottle Warmer: A bottle warmer is a convenient and quicker way to warm breast milk. Most bottle warmers have a setting specifically for warming breast milk, so follow the manufacturer’s instructions.

How to Properly Express Breast Milk and Storage Guidelines/Tips

Expressing Breast Milk

  1. It is best to express milk when the breasts are full or engorged. Read more about power pumping here.
  2. Use a clean and sterilized breast pump. For hand expression, ensure your hands are clean.
  3. Massage the breasts gently before expressing to help stimulate milk flow.
  4. Express milk until the flow slows down or stops.
  5. Be sure to record the date and time of expression on the container or bag.

Breast Milk Storage Guidelines

  1. Always ensure your hands and the containers or bags you use to store the milk are clean.
  2. Use a breast milk bottle(s) or purpose-specific bag(s). Use only BPA-free containers.
  3. Store the milk in small amounts, so you can use it at once or within the two-hour time frame.
  4. Avoid storing milk in direct contact with the freezer walls or door, as this can cause the milk to freeze unevenly and potentially damage the milk’s quality.
  5. Avoid storing milk in the door of the refrigerator or freezer, as this area is subject to temperature fluctuations. Ensure that it is tucked safely in the freezer compartment.
  6. Use up the oldest milk first.
  7. When thawing frozen milk, it is best to keep it in the refrigerator for a while. If urgent, place the container under running water and increase the temperature slowly at intervals.
  8. Avoid using a microwave to thaw breast milk as it can cause hot spots and damage the milk’s nutrients.
  9. Never refreeze thawed breast milk. Simply dispose of leftover milk.
  10. Storing breast milk allows you easy access to milk when your baby demands it. Moreover, if you store breast milk correctly, it can last up to 6-12 months in the freezer.

Should I Mix Hot and Cold Milk?

While this is tempting, you should not mix hot or freshly expressed breast milk with a cold one. It can affect the quality and safety of human milk.

The reason is simple. Bacteria grow and thrive faster in warm temperatures. Mixing warm and cold milk will increase the temperature of the cold one, providing the ideal environment for bacterial growth.

If you must mix freshly pumped milk with a cold one, put both in a refrigerator first. While the former drops in temperature, the latter rises. After a few hours, you can proceed to pour the contents of one into the other.


Knowing how long breast milk lasts after warming, how to warm it up properly, and the best methods to store it are crucial in ensuring the safety and quality of the milk for your baby.

While there are alternative methods of storing expressed milk such as insulated cooler bags, and room temperature storage, traditional methods like refrigeration and freezing make it last longer.

Do not leave frozen milk out by itself. You can submerge it in water. If there are no more ice crystals, you can put it aside until it comes to room temperature and use it within two hours.

Also, proper hygiene practices, including washing hands, using clean and properly sealed containers or bags, and using the oldest breast milk first are all vital to keep your milk safe when you give it to your child.

Quick summary: Warmed milk can last up to two hours, while freshly pumped milk stored in a cool, dry place can last up to four hours.

Written by

Anna Thornhill
Anna Thornhill
Anna is one of our expert writers and, as a mom of two lovely kids (a daughter and son), she has plenty of practical experience to draw on when writing guides and reviews. Anna writes about techniques she's used both during pregnancy and as a new mother, such as combination feeding, and guides to products that have made feeding and care of her kids a little easier.


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