I often get asked about the safe handling storage of breast milk as well as formula. So let’s break it down:

Breast milk is a living substance with digestive enzymes that help break down milk in baby;’s digestive tract. It’s also full of live immune properties to help baby fight infections, bacteria and viruses. Formula is FOOD. I know that seems obvious, but it’s really important to remember. Since it is food, we have to follow food safety rules when preparing, using and storing formula. Breast milk is also a food, but like all foods, they have unique storage properties based off of what the food is and the risk of contamination and spoiling. So the rules for formula and breast milk are similar, but different. The rules for formula help prevent bacterial contamination which can make your baby sick. Keep in mind that these are guidelines. You know your home situation best, which includes your water source, what else is living in your refrigerator, the climate you live at, and your own cleanliness in the kitchen.

Let’s talk about formula first. Prepared formula, meaning mixed powdered formula that you made with water following the manufacturer’s instructions but that has not come into contact with your baby’s mouth, can be stored in the fridge for 24 hours at an ideal temperature of 37 degrees Fahrenheit.  Ready to feed formula that hasn[‘t been offered can actually be stored inthe feridge for up to 48 hours, ideally in an air-tight storage container. This is stored in the back of the fridge where it is coldest and least likely to be impacted by temperature fluctuation that happen near the door of the fridge. This does mean that if you are offering more than one bottle of formula per day you can mix your entire day’s worth of formula in the mourning, store it in a pitcher,and pour out of the pitcher into your bottle volumes to heat and feed. This can save you time when your baby is really hungry. You also want to make sure all of your containers for storage are air tight to prevent that formula from absorbing odors from other foods in the fridge.

2 hours. That’s how long you have for formula to sit at room temperature once it’s been mixed, as long as it hasn’t touched your baby’s lips. That means you can mix up a bottle before you leave the house and leave it in your diaper bag to be fed within two hours of leaving the house.

Once that bottle of formula has touched your baby’s lips, you have to use it within 1 hour or you need to toss it. This is because bacteria from your baby;’s mouth is introduced back into the bottle (thanks baby back wash) and the bacteria can multiply and grow to unsafe levels. Health care providers will always recommend safest practice to help keep your little one healthy.

Worried about wasting formula? Here are a few tips: Mixing formula in a pitcher means you can pour out just enough for the feeding. If baby is still hungry, you can pour small amounts for top ups to prevent mixing too much and wasting formula. If your baby has a little formula remaining in the bottle and you know they will want a top off later, consider offering the bottle again at the 50-minute mark before the bottle expires.

So what about freshly pumped breast milk? There are other rules that apply:

• Use breast milk storage bags or clean, food-grade containers to store expressed breast milk. Make sure the containers are made of glass or plastic and have tight fitting lids.
  • Avoid bottles with the recycle symbol number 7, which indicates that the container may be made of a BPA-containing plastic.
• Never store breast milk in disposable bottle liners or plastic/ziplock bags that are not intended for storing breast milk.
• Freshly expressed or pumped milk can be stored:
  • At room temperature (77°F or colder) for up to 4 hours.
  • In the back of the refrigerator away from the door for up to 4 days.
  • In the freezer for about 6 months is best; up to 12 months is acceptable. Although freezing keeps food safe almost indefinitely, recommended storage times are important to follow for best quality. Freeze your milk flat to save space and make sure to store int he back of the freezer where it’s coldest, away from the door where temperature can fluctuate.
• If you don’t think you will use freshly expressed breast milk within 4 days, freeze it right away. This will help to protect the quality of the breast milk. The longer breast milk sits out, the more the live digestive enzymes in it will break down the nutrients in your milk.
• When freezing breast milk:
  • Store small amounts to avoid wasting milk that might not be finished. Store in 2 to 4 ounces or the amount offered at one feeding.
  • Leave about one inch of space at the top of the container because breast milk expands as it freezes.
  • Breast milk can be stored in an insulated cooler with frozen ice packs for up to 24 hours when you are traveling. At your destination, use the milk right away, store it in the refrigerator, or freeze it.
• Make sure to test for lipase before storing large batches of breast milk in the freezer. Lipase is the enzyme that breaks down the fat in breast milk. For some people with high lipase, their milk can taste soapy or metallic when stored. Some babies are fine to drink this milk and others may refuse it. See my other posts and videos on high lipase and what to do about it.
• Always thaw the oldest breast milk first. Remember first in, first out. Over time, the nutrients in breast milk start to break down. When at all possible, feed fresh milk.
• Breast milk can be defrosted in the fridge, normally in around 12 hours. Alternatively, hold the bottle or bag of frozen milk under warm running water (a maximum of 37 °C or 99 °F). Don’t leave frozen breast milk to defrost at room temperature. If you forget it on the counter for too long, past safe feeding guidelines, you may lose that batch of milk. And we cry over spilt and lost breast milk.
• Never thaw or heat breast milk in a microwave. Microwaving can destroy nutrients in breast milk and create hot spots, which can burn baby’s mouth.
• If you thaw breast milk in the refrigerator, use it within 24 hours. Start counting the 24 hours when the breast milk is completely thawed, not from the time when you took it out of the freezer. If there are still ice crystals felt in the milk, it is still considered frozen.
• Once breast milk is brought to room temperature or warmed, use it within 2 hours.
• Never refreeze breast milk after it has thawed.
• Breast milk does not need to be warmed. It can be served room temperature or cold.
• If you decide to warm the breast milk, here are some tips:
  • Keep the container sealed.
  • Place the sealed container into a bowl of warm water or hold it under hot, running water for a few minutes.
  • Test the milk’s temperature before feeding it to your baby by putting a few drops on your wrist.
• Swirl or shake the breast milk to mix the fat, which may have separated. Fat separation is normal for breast milk. There used to be an old wives’ take that shaking the milk could some how damage the milk. We’ve debunked that for years. If you’re concerned about the bubbles that form from shaking giving your baby gas, you can swirl or stir it as well.
• If your baby did not finish the bottle, use the leftover milk within 2 hours after the baby is finished feeding. After 2 hours, leftover breast milk should be discarded. Yes, you get a longer amount of time to offer breast milk in a bottle than formula.

Finally: If you’re mixing breast milk and formula together in the same bottle: Formula rules apply, meaning once that bottle has touched baby’s lips, you only have one hour to feed it to the baby.