Experts say there are some surefire signs that your breast milk has gone bad.
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5 Signs Your Breast Milk Has Gone Bad

And how to prevent it from ever spoiling again.

by Olivia Youngs and Ashley Jones
Originally Published: 

There's nothing worse than spending so much time pumping your breast milk only to find out that it's gone bad sooner than you expected. Luckily, it’s not hard to determine if your milk has gone bad, and knowing the signs can save you from the pain of having to pump your milk just to dump it a few days later. After all, the stuff is called liquid gold for a reason — no mom wants to have to throw out even one solitary drop of her hard-won milk.

Not unlike cow's milk, breast milk will spoil if left out in the open, or even in the refrigerator for longer than it should be, according to guidelines from The Centers for Disease Control and Prevention (CDC). “For full-term healthy infants, the recommendation is no longer than four hours at room temperature for freshly expressed breastmilk and one to two hours for thawed breast milk,” Molly Petersen, a Certified Lactation Counselor (CLC) at Lansinoh tells Romper.

This timing changes, however, once the milk has been stored in the fridge or freezer after pumping. Lactation consultant and Motif Medical Lactation Director, Ashley Georgakopoulos, tells Romper that pumped breast milk lasts about four days in the refrigerator. Additionally, Georgakopoulos notes that breast milk can be “frozen up to four months in a regular freezer, or up to 12 months in a deep freezer.” After you remove it from the freezer, the timing changes once again. “Once it has thawed and all the ice crystals have been melted, it needs to be used within 24 hours before being discarded, and refrigerated in between use, as it only can stay out at room temperature up to two hours,” she tells Romper. Knowing how long breast milk can stay in the fridge is a huge part of making sure your stash doesn’t spoil.

Following these recommendations is the easiest way to make sure that your milk doesn’t spoil. But, if you lose track of time (which happens often as a new mom), there are a few ways to tell whether or not your breast milk is spoiled.


It Will Smell Foul

Foul-smelling breast milk can indicate that your milk has gone bad. When this is the case, it will smell similar to rotten cow’s milk — that can’t-stand-it-being-anywhere-near-your-nose type of smell that makes you want to gag.

But breast milk that smells “off” doesn’t always mean it’s spoiled. “Breast milk can break down and release certain odors from enzymes,” Georgakopoulos says. “This can be anything from a metallic smell to a soapy smell, and generally does not mean that it has gone bad. Most of the time, this does not affect the way baby will take it in, but some may be offended by the smell.”

When in doubt though, Georgakopoulos says you’re better off safe than sorry when your milk doesn’t pass the sniff-test. “If it smells like spoiled milk or is questionable in any way, it may be best to throw it out,” she explains.


It Doesn't Mix When Swirled

“Breast milk naturally separates as it settles, and can be mistaken for going bad as the fat goes to the top. It may be mistaken for curdling/souring,” Georgakopoulos says.

While swirling it around should do the trick to re-constitute the milk, if your breast milk doesn't mix when swirled, or if there are chunks in the milk that won't mix, it’s worth a closer look to make sure that your milk has been stored properly and it’s not spoiled. “You can’t always tell if milk is still good just by looking at it, smelling it, or even tasting it,” Petersen says. “So it’s best to adhere to the recommended storage guidelines as closely as possible to ensure the safety of your milk.”


It Sat In The Fridge For Longer Than 4 Days

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“Fresh breast milk can be refrigerated up to four days, but if it has been drunk out of, it needs to be used within 24 hours,” Georgakopoulos explains. Only pour into a bottle what you think will be used just to be safe.

Breast milk that’s been in your fridge for longer than four days is likely not usable. For maximum shelf life, store your milk in the "heart" of your fridge and not in the door, where the temperature fluctuates the most.

To help you keep track of time, it’s important to label all of your pumped breast milk. “All milk storage containers should be labeled with the date the milk was pumped,” Petersen says. “This will allow you to set up a system to ensure the oldest milk gets used first.”


It Wasn't Stored Properly

Like anything, if your breast milk wasn't sealed or stored properly or the bag or container had a tear in it, the chances of your milk spoiling greatly increase. “When storing breast milk in the fridge or freezer, it’s important to use a container that is specifically designed for breastmilk storage,” Petersen says. “These breast milk containers are made with plastics that are safe and designed to stand up to storage conditions.”

Label your breast milk with the date and take note of what the guidelines are as mentioned above for the way that you’re storing it in order to help ensure that your milk stays fresh. If you’re storing it in the freezer, put it in there as soon as possible after pumping, and store it in the main part of your freezer instead of the door. “Many moms may be pumping at work or another place away from home, and in those cases, you should cool the milk in the fridge or a cooler bag as soon as possible after pumping,” Petersen says. “Once you are home, transfer milk to the freezer.”

To thaw your frozen breast milk, Petersen says the best way is to put it in the fridge overnight. “If you need it quickly, storage bags can be run under warm tap water or sat in a bowl of warm water for a few minutes for a fast thaw,” she says. “Remember once milk has been removed from the freezer, it needs to be used within 24 hours.”


It Tastes Sour

Obviously, the easiest way to tell if your milk is sour is to taste a bit of it yourself.

“A sour taste can indicate if it has gone bad,” Georgakopoulos says. “Smelling is safer, but safe handling and good inventory is usually the best way to go, since breast milk does, in fact, keep very well.”

Remember though, your breast milk can still taste “off” to you due to the enzymes breaking down. But Georgakopoulos just recommends that “if in doubt, throw it out, or use topically.”


Ashley Georgakopoulos, Motif Medical Lactation Director & IBCLC

Molly Petersen, Certified Lactation Counselor (CLC) at Lansinoh

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