How to Defrost Breast Milk

Keeping Baby Safe: Thawing Breast Milk Safely

Breast milk is sometimes referred to as “liquid gold,” because it's so important to your baby's health. Plus, breastfeeding is hard work, and every drop counts. If you freeze your breast milk for future use, defrost it safely so you don’t waste any. In addition to thawing it safely, you want to prep it for your baby carefully to avoid any contamination or loss of vitamins.

Storing Breast Milk

breast milk in the bottle and storage bags on red towel

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Once you pump your breast milk, you must store it carefully. Keep the milk in bottles with caps, plastic cups with tight lids or bags designed specifically for storing breast milk. Using other bags to store your milk might result in leaks or spills, and the risk of contamination is greater.

Label your milk with the amount and the date you pumped it. Keeping track of the date allows you to know which milk to use first. If any of the milk is going to a child-care provider, label it with your little one’s name.

Recommendations vary, but some guidelines for safe storage of breast milk include:

  • Room temperature for 4 to 6 hours as long as it’s covered and kept as cool as possible.
  • Insulated cooler bag for 24 hours with ice packs in constant contact with milk containers.
  • Refrigerator for up to five days, placed in the back and not in the door.
  • Freezer within a fridge for two weeks, but kept away from the sides of the freezer, toward the back.
  • Freezer attached to a refrigerator, but with its own door, for three to six months, but kept toward the back away from the freezer's sides.
  • Deep freezer for six to 12 months, but away from the sides of the freezer, toward the back.

Thawing Breast Milk

You can thaw breast milk a couple of different ways, depending on whether you’re in a time crunch. First, make sure you thaw the oldest breast milk before any newer milk. Take the milk out of the freezer and put it in the fridge about 24 hours before you need it. If you don’t have time for that, you can run it under warm water or swirl it in a bowl of warm water.

Don’t use a microwave or stove to thaw your breast milk. The microwave doesn’t heat the milk evenly; the bottle may explode if it’s left in the microwave too long; and the excess heat can destroy some of the nutritional quality of the milk.


After you've thawed breast milk, don't refreeze it.

Warming Up Breast Milk

breast milk in the bottle and storage bags on red towel

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You can warm your breast milk under warm running water or put it in a pan of water that has already been heated. You can also use a bottle warmer. Squirt a few drops of the heated milk on your wrist to check the temperature before giving it to your little one. It should feel lukewarm.

Don’t be surprised if your thawed milk looks a little different from when you first pumped it. It’s normal for the milk to separate into a milk layer and a cream layer when stored. Just swirl it around to mix it before you give it to your baby. It also may smell different, which isn’t an issue.


  • To prevent contamination, wash your hands before you express or handle your breast milk.
  • Make sure to give your little one any heated milk within an hour or two of warming to avoid contamination. Bacteria in your baby’s mouth can enter the bottle while she’s drinking and grow in the milk. Milk has antibacterial properties that slow the growth, but it’s still best not to save the milk too long.
  • Don’t fill breast milk containers to the top; instead, leave at least an inch of space. Breast milk expands as it freezes, and you may have a mess on your hands if your milk overflows.
  • You can add fresh milk to previously refrigerated or frozen breast milk, but cool the fresh milk completely first. If you don’t, it may cause the frozen milk to start to thaw.

Feeding Your Baby

Make sure you’re using the right size nipple when you give your baby a bottle. If your little one is gagging or gulping, try a slower flow nipple. If he seems frustrated, try a faster flow nipple.

Take the bottle away before your baby falls asleep, especially if he’s cutting teeth. Milk that pools in your little one’s mouth can cause tooth decay. Gently wipe away any milk residue with a soft cloth when your little one has finished the bottle.

Make giving your baby his bottle an excuse to spend extra time cuddling with him. It may be hard to find the time, and you may be tempted to just prop the bottle and get a few extra things done. However, propping the bottle isn’t safe. Your little one could choke, or the bottle could fall. Additionally, propping the bottle increases the risk of ear infections.