Experts say thawed breast milk can last an hour or two at room temperature.
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Here's How Long Thawed Breast Milk Really Lasts, According To Experts

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Whether it's formula or breast milk, throwing out a bottle is the worst. It's either money down the drain or, if you're breastfeeding, time and hard work down the drain.You probably know to thaw only what your baby will drink, but how long does thawed breast milk really last? What if your baby doesn't finish their bottle? Do you really have to toss out a whole 6 ounces of liquid gold?

The answer truly depends on where you store your breast milk once it has thawed, but as a general rule, Jennifer Ritchie, an International Board Certified Lactation Consultant (IBCLC) and author of The Smart Parents Guide To Breastfeeding recommends using thawed breast milk as soon as possible.

If storing in the refrigerator, Ritchie tells Romper, “Once frozen milk has been thawed, it must be used within 24 hours or discarded.” If your milk has been sitting out at room temperature (77°F, 25°C, or colder) say, on a countertop or table, Ritchie says that the Centers for Disease Control and Prevention (CDC) “recommends discarding after one to two hours.”

It's also important to remember that these numbers change once the baby has started to drink the bottle. “If your baby did not finish the bottle, the leftover breast milk can still be used within one to two hours after the baby is finished feeding,” Ritchie says. “After two hours, leftover breast milk should be thrown away.”

Even if your baby only drank an ounce of the bottle, unfortunately, you can't keep it stored in the fridge or re-freeze it either. “Milk that has fully thawed should not be refrozen due to the risk of bacterial contamination,” Ritchie says.

To eliminate the amount of breast milk waste you might end up, use the “first in, first out” method, thawing the oldest breast milk in your freezer first. “Fresher breast milk is almost always most ideal for baby from a protective standpoint, but to reduce waste, moms that are using a freezer stash will usually want to thaw the oldest first,” nurse and lactation consultant Angie Natero tells Romper. “Milk can usually be thawed overnight in the fridge.”

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You can also help reduce waste by keeping your breast milk stored in portions your baby will eat, and thaw only one day's worth of breast milk at a time to make sure you aren't pouring too much of it down the drain. “Milk should be frozen in plastic bottles or plastic bags specifically designed for breast milk storage. Regular Ziploc type plastic bags are not recommended,” Ritchie explains. “Freeze milk in the amount that the baby would normally eat so that once it is thawed, none is wasted.”

Another time when it might be tempting to toss thawed breast milk is if you notice changes to your milk after thawing. However, this isn’t necessarily something to be concerned about. “Sometimes there are slight changes in the taste and smell of milk that has been frozen due to the enzymes naturally present in breast milk,” Ritchie says. “Those changes are not harmful, however some babies do have a noticeable preference for milk that has not been previously frozen.”

When dealing with frozen breast milk that you plan to thaw and feed your baby, it’s important to make sure that you know how to properly handle storing the milk. This is especially true during unexpected circumstances like a power outage, which can impact your frozen breast milk.

“Do not open your freezer unless necessary,” Ritchie says. “If the power is out for 12 hours or more, you will need to start either transferring your milk to another freezer with power, packing milk in a cooler with ice, or packing your freezer with ice to keep your milk from thawing.”


Jennifer Ritchie, IBCLC and author of The Smart Parents Guide To Breastfeeding

Angie Natero, RN IBCLC

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