How Long Can Breast Milk Sit Out?

Keeping Breast Milk Safe for Your Little One

Follow safe breast milk storage guidelines about keeping the milk at room temperature to avoid spoiling.

Anyone who has ever expressed breast milk respects the amount of work you go through to pump those precious ounces. And you don't want even one drop to go to waste or make your baby sick. Brushing up on your breast milk storage guidelines to be clear on how long breast milk can sit out.

Freshly Expressed Breast Milk

You're finished with the tedious task of pumping, and you have those valuable bottles of milk awaiting storage. Do you have time for a little break before you put it in the refrigerator or feed your little one? You sure do.

Ideally, you should refrigerate or use your breast milk within four hours if you keep it at room temperature. Your breast milk is safe at room temperature for up to six hours unless the room is particularly hot, in which case it needs to be used in no more than four hours. The increased temperature encourages bacterial growth, which can make the milk go bad.

So go ahead and take a quick nap, answer a few emails or enjoy some quality play time with your little one. Set a timer for four hours, and you reduce the risks of the milk going bad.

Refrigerated Breast Milk

Once you refrigerate breast milk, the guidelines become less clear. Refrigerated breast milk is best used within three days of pumping, but it's generally safe for up to five days if it is stored in clean conditions at the back of the refrigerator. Breast milk has a significant drop in its ability to fight off bacterial growth after 48 to 72 hours of refrigeration, but the bacterial growth is still low and in the safe range in most cases for several days.

Once you remove the milk from the refrigerator, the bacterial growth potential varies. If the milk is only one or two days old, it likely still has antibacterial qualities and can sit out for a short while. If more time has passed since you expressed the milk, the liquid may be more susceptible to growing bacteria once you take it out of the refrigerator. It's best to leave the milk in the refrigerator until you're ready to feed your little one or move it to the freezer.

Frozen Breast Milk

Freezing breast milk lets you store it safely for several months. Although the antibacterial traits of breast milk may drop off after being in the freezer for three weeks, most nutrients will remain in the breast milk for up to three months in the freezer. The milk can be safely stored for as long as 12 months, but it may not have as many nutrients in it. Aim to store frozen breast milk no longer than six months.

Pop the frozen breast milk in the refrigerator overnight for the safest way to defrost it. If lack of sleep makes you forget, it's also safe to defrost the milk in a bowl of warm water. As tempting as it is to quickly zap the milk in the microwave, it loses at least some of its infection-fighting power after being nuked. It's also tough to heat the milk evenly.

Since frozen milk loses a lot of its antibacterial strength, it's best to use it as quickly as possible. The defense against bacteria drops significantly after being thawed for 24 hours. Don't leave the thawed breast milk out at room temperature for more than a few hours, as the risk of bacterial growth increases significantly.

Warmed Breast Milk

Several factors impact the potential for bacterial growth in warmed breast milk. Has it been frozen? Did you thaw it more than 24 hours ago? Has it been in the refrigerator for longer than two or three days? How did you warm the milk? The older the breast milk, the less resistance it has to bacteria, which means it could go bad if it sits out for too long.

Once you start feeding your little one the warmed milk, bacteria from your baby's mouth can potentially get into the breast milk. There's no solid research on this scenario, but experts feel that partially used breast milk should stay safe at room temperature for an hour or two.

How Do You Know if Breast Milk Is Bad?

You can't see the bacterial growth, so you have to rely on what you can see and smell. Keeping track of when you pump the milk helps determine whether or not it is still good. Mark the bottle with the date if you're storing the milk in the refrigerator or freezer. If you add more breast milk to the same bottle later, keep the earliest date on the container.

Smelling the milk can tell you if it's bad. Spoiled breast milk has a strong odor. If you're up for a taste test, you know the milk is bad if it has a sour taste.

Safe Storage Guidelines

Storing breast milk safely maximizes how long you can save it while keeping your little one healthy. Use these additional guidelines for safe storage:

  • Wash your hands before handling breast milk containers or breast pump parts.
  • Use containers designed for milk storage.
  • Wash bottles thoroughly before storage to prevent contamination.
  • Feed your baby the milk within the recommended time frame.
  • Store milk at the back of the refrigerator or freezer to keep it cold and avoid temperature changes when you open the door.
  • If you add more milk to a container in the refrigerator, cool the new milk first. 
  • When in doubt, throw away milk that you feel may be contaminated.
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