September 20, 2023

How To Store Your Breast Milk Safely

Typically, you’ll want to store 2 to 4 ounces at a time

preparing frozen breast milk for baby

The old adage says there’s no use crying over spilled milk. But when it’s milk for your little one, it’s sad to see any go to waste.


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With proper planning, you can prevent wasting any breast milk (chest milk) you’ve pumped to nourish your baby or toddler. And if you’re getting your supply from a breast milk donor bank, knowing how to store milk is key to making sure your little one is fed.

So, how long will it keep in the fridge or freezer? What containers should you store it in? And what’s the best way to thaw it? Pediatrician and breastfeeding medicine specialist Heidi Szugye, DO, IBCLC, explains all the reasons you may want to store breast milk, along with tips for making sure it’s good enough for your child.

What are the benefits of storing breast milk?

If you’re hand-expressing your breast milk or pumping, it’s good to know how to store the milk you produce. Storing your milk allows you to have some ready for whenever your child has their next feeding. Plus, it’s important to know how to store your milk so it stays fresh and maintains its nutritional properties and immune-system boosters.

Even after you’ve used up your colostrum during your earliest feedings, human milk is as beneficial as formula when it comes to nutritional value, especially during your infant’s first six months of life. And if you’re unable to produce breast milk on your own, human milk banks are a helpful resource that collects, screens, stores, processes and distributes milk for parents in need.

How can you store breast milk safely?

Breast milk can be kept at room temperature, in a refrigerator or in a freezer — and how long you can store your milk safely depends on its location and the containers you use.

In most cases, you’ll want to store 2 to 4 ounces of breast milk at a time. On average, this is the amount of milk that your baby consumes in a single feeding. Storing a smaller amount of 1 to 2 ounces can also be helpful for when you need to provide a smaller snack or for babies fewer than 6 weeks old.

Containers you can use to store milk include:

  • Glass is the first choice for breast milk storage. It preserves the components of milk the best. But glass breaks, so keep in mind that some daycare centers won’t allow it.
  • Hard-sided plastic containers are the second-choice alternative for breast milk storage. Look for BPA-free and opaque or clear plastic options. The U.S. Centers for Disease Control and Prevention (CDC) states you should never use bottles with BPA because of its microplastic and chemical content. You’ll know if it contains BPA if it’s labeled with the recycle symbol number 7.
  • Breast milk freezer bags or nursing bags are best for storage in the freezer. While freezer bags are convenient and space-saving, they have the most opportunity to leak. To avoid damage, place your bags in firm plastic containers or double bag it if it’s a thinner storage bag.

When storing milk, it’s important to label each container with a smudge-proof marker with the date expressed and the amount of milk in each container. Use the oldest milk first to keep your supplies fresh and avoid expired or sour milk. If you’re delivering stored milk to childcare, you should also label the container with your child’s name to avoid mix-ups.


How long will breast milk keep fresh?

Storing smaller amounts can be useful, as they can be warmed quickly and may help cut down in the amount you throw away. This is particularly important when it comes to milk that you’ve frozen and then thawed: Thawed or warmed milk has a much shorter shelf life than when it’s refrigerated. So, once you remove it from a cool environment, the clock starts ticking.

Milk can be stored:

  • Up to four days in a standard refrigerator.
  • Up to three to four months inside a standard refrigerator freezer.
  • Up to six to 12 months in a separate deep freezer.
  • In an insulated cooler bag with frozen ice packs for up to 24 hours while traveling.

You want to avoid storing milk in the door of your refrigerator or freezer and store it at the back instead to avoid frequent temperature changes. The other thing to consider while freezing is that sometimes your milk may look differently than you expect.

It’s normal for stored milk to separate into a cream and milk layer. It’s also normal for breast milk to appear in a range of colors from slightly yellow to yellow-orange and even green. The color of your breast milk can change based on what you eat, drink and the medications you take while breastfeeding. If you’re ever concerned about the color of your stored milk, a lactation consultant can offer some direction on what’s safe to use.

The amount of time you can keep breast milk out at room temperature depends on how warm the surrounding environment is and whether or not the milk is freshly expressed or if it’s been previously frozen and then thawed and/or warmed for feeding.

At room temperature (77 degrees Fahrenheit, 25 degrees Celsius), breast milk should be used:

  • Within four hours if it’s been freshly expressed or pumped.
  • Within two hours if it’s been refrigerated or frozen and then thawed.

You never want to keep milk at temperatures higher than 77 F (25 C) because of the risk of bacteria growth. Once your milk has been frozen and thawed, you also never want to refreeze your milk.

“To be safe, discard any previously frozen milk that’s been heated and served to your baby after one to two hours,” advises Dr. Szugye. “Refreezing milk can lead to contamination, so you never want to refreeze milk that’s been thawed.”


How to thaw frozen breast milk

A child can drink cold or room-temperature milk, but they may like it better if it’s warm. When warming milk, you never want to use a microwave or directly use a stovetop or oven. A microwave doesn’t heat breast milk evenly, and if the milk is too hot, it can scald your baby. Heating milk too quickly or at higher temperatures can also destroy important proteins and vitamins in the milk. In some cases, it can also cause the bottle to explode if it’s heated for too long. Also, never bring your milk to a high heat or boiling point.

To thaw and warm frozen breast milk, start by holding the container of frozen milk under warm, running water for a few minutes. You can also heat a pan of water on the stove over low-to-medium heat, remove it from the stove after a minute or two, and then soak your freezer bag in the pan of warm water for several minutes.

When soaking, you’ll want to make sure the water doesn’t go over the top of the bag or make contact with the seal in order to avoid contamination. If your milk looks cloudy while warming, there’s been a leak and the milk is no longer good.

You can also use a bottle warmer if you have one.

Once the milk has been warmed, swirl the separated cream and milk layers together. Test the milk’s temperature by putting a few drops of milk on your wrist — if it feels slightly warm but not hot, it’s safe to use for feeding.

If your child doesn’t finish the entire container, you can use the leftover milk within two hours of warming. After two hours, you should discard any leftover, previously thawed milk.

Breast milk has many nutrients tailored to your baby’s growing needs,” says Dr. Szugye. “With a little planning, you can continue providing for your baby throughout their infancy.”

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