How Long is Breast Milk Good for After Warming?

Pumping and storing breast milk is a painstaking process, so naturally, you don’t want to waste any of the precious ounces.

But what if you have already warmed the chilled or frozen packet of milk and your baby didn’t finish it? Can you use it if it’s been sitting out or do you toss it?

We’re going to consult a few experts to see what they suggest. Then we’ll give a quick rundown of best practices to ensure your milk stays safe to consume for as long as possible.

Breast milk is a living food, full of nutrition as well as a certain level of bacteria. The milk itself has inherent antibacterial properties which keep the harmful microbes in check. Under normal circumstances, breast milk can be safely stored for up to eight days in the refrigerator.

But this applies only to freshly expressed milk, not milk that has been stored then rewarmed. The question we’re asking is how long after warming the milk is it safe for your infant to consume it. In other words, how fast till it spoils?

To date, there are no published scientific studies which specifically address the safety of offering previously warmed milk to your child. Frankly, there are breastfeeding advocates with opposing opinions.

Some say, yes, you can use warmed milk for some time after it has been warmed for initial consumption. This article suggests that you put any unused milk back into the refrigerator within half an hour of warming to be heated up later.

In this article by the lactation consultant, Jan Barger, she cites a small study stating there is little difference between first-time warmed milk and using the same milk later. 

Ruth Lawrence, MD, states the following on page 639 in her book, Breastfeeding: A Guide for the Medical Professional:

“[Fresh] Breast milk can safely stand at room temperature for 6 to 8 hours and need not be discarded if the first feeding attempt is incomplete.” (7th edition, 2011)

The Academy of Breastfeeding Medicine Protocol Committee suggests that whether human milk is safe to consume after being thawed depends on how the milk was collected, how it was thawed and, of course, how much bacteria was in the milk.

The problem is that, as stated above, there are no studies showing whether or not warmed breast milk is unsafe after sitting out for a certain period. As such, many experts warn mothers to throw away any unused milk.

Both sides have their points. You will have to use your own judgment as well as your nose to decide if the milk is safe for your child. You can give the unused portion a sniff test. Breast milk generally has a light, sweet scent. If it has a sour smell, play it safe and toss it.

In the event that you choose to warm up and offer your infant previously thawed/warmed milk, there are times you should not risk using it. Never feed rewarmed milk to a child with a compromised immune system such as a preemie or when your infant is ill.


But What About Wasting All That Precious Milk?

There are two ways to handle this so milk won’t be wasted. One way is not to thaw any more than you need at each feeding. Don’t worry that you didn’t warm up enough since heating up milk only takes a few minutes.

Alternatively, for those who are less concerned about offering warmed milk, consume it within a half an hour or immediately put in refrigerator for later use.

Best Practices for Handling Breast Milk for Optimal Storage Life

There is no need to be paranoid but since the health of your child is paramount, you will want to be careful with hygiene and milk storage practices. Here are some quick reminders:

Before pumping:

  • Wash your hands. No need for any sterilization – just hot water and soap
  • Make sure your nursing bra is changed often, also your breast pads
  • Use only new, clean packets for storing milk
  • Save smaller portions per packet, especially during early infancy
  • After pumping:

  • Label with date each packet
  • Store milk in the back of the refrigerator or freezer where it is coldest
  • See more here

    Wash pump parts which came in contact with your skin in hot, soapy water and air dry, perhaps you could even use some specialized breast pump cleaning wipes

    Ultimately, you will be the best judge of whether to reuse breast milk which has been standing out of the refrigerator. But as the old adage says, “When in doubt, toss it out.” In the end, your child’s health is more important than quibbling over wasting a few ounces of milk.

    (This article has been used with permission from