Human Milk Storage
There is SO much available information out there on how to safely feed your baby. Here’s a snapshot of it.
The CDC is responsible for making recommendations for everyone all over the world, including places where folks are rightly concerned about the sanitation of their water and feeding environments. Keep this in mind when it comes to how closely you follow their guidelines, and consider a bit more leniency if you are rightly NOT as concerned about the cleanliness of your home, bottles/pump parts, or water. This is particularly true if you are a warrior dealing with an undersupply. Overall, feeding your baby the freshest milk possible is of course the “ideal.” AND. Here at Toula Co, we recognize that we do not always get to live in an ideal world; we live right here with you in the real world. We are also, however, not in the business of carelessly throwing human milk away, EVER. The following guidelines are meant to help you protect every precious drop!
The ONLY human milk I will recommend that you throw away, EVER: Milk that is obviously rancid and smells bad. No, I’m not joking.
Human Milk Storage Guidelines
General rule to remember: 8-8-8
Human milk is DESIGNED to fight bacteria; it is actively working to keep itself safe for your baby’s consumption from the moment it is expressed. If the milk is expressed into clean containers in a clean environment, the main thing we are concerned about is NOT the safety of feeding the milk to your baby, but rather trying to maintain as much nutritional value as possible.
Freshly Expressed Milk can stay at room temperature before being fed to baby, refrigerated or frozen for up to 8 hours.
This means that if you pump during the middle of the night, you certainly do not need to get up and put your milk directly in the fridge, or even in a cooler, as long as you take care of it or feed it to baby within the next 8 hours. If you have the resources (time, energy, money) to be extra careful, you might use a chiller like this at your bedside! Just fill the tumbler with ice before you go to bed, and you’ll even further elongate the freshness of your milk. You can even pump directly into the chiller.. then get your butt back to sleep.
DO consider if the milk is sitting in a warmer place, like near a heating vent or in direct sunlight, and know that this shortens the time that it should be left out. The cooler the place, the better and longer it’s okay to stay.
Milk can stay in in the refrigerator before being fed to baby or frozen for up to 8 days.
DO consider where in the fridge you’re storing your milk. Milk kept in the refrigerator door, for instance, will come in contact with a lot more room temperature air than milk stored at the back of the refrigerator. Again. Cooler = longer.
What should you use to store your milk in the fridge? In the interest of the environment, I do NOT recommend using single-use plastic storage bags (yes, even for freezing, more on that below). Instead, consider these reusable options!
If you want to really organize your life, consider this bottle and storage tray set from Medela that helps you keep track of what day the milk is from, and which bottle should be used next (but… read in FAQs about whether the “AM/PM” indicator is really necessary).
Another option is pooling your milk in a pitcher like this! There is NO research to support the notion that combining/pooling milk at different temperatures is damaging to your milk!! Simply write the EARLIEST date of milk that’s in the pitcher on the lid or side with a Wet Erase Marker, continue to fill and use milk from the pitcher for about 8 days, then freeze any remaining milk and wash the pitcher! Repeat.
Wet Erase Markers are also a great tool to use for labelling smaller individual bottles of milk instead of more wasteful single use techniques like masking tape!
Here’s a glass pitcher option without a stirring rod. You just might need to gently reincorporate the fatty layer of your milk with a long spoon before pouring!
Milk can stay in the freezer for up to 8-12 months.
In the interest of the environment, I recommend considering freezing your milk in glass jars like these, or reusable silicon bags like these! I do not recommend silicon bags with more narrow pour spouts - SO tough to clean and fully dry! Simply use the same Wet Erase Markers from above to label your milk, or place them in larger tupperware containers with labels on them! (i.e. “June 2025” milk on one large container instead of labeling each individual bag/jar). Be sure to leave a bit of room at the top of your jar, with the lid SLIGHTLY loose until the milk is fully frozen, then go back in and tighten the lid.
Similarly to refrigerator storage, consider WHERE in your freezer you’re keeping your milk. The deeper and less disturbed, the longer it will last! If you have the space and resources, you might consider investing in a deep freezer.
HOW to freeze your milk: if in bags, flat and in amounts of 3-4oz, or in smaller amounts of 1oz in trays like these, to then be removed and stored in a separate Tupperware container - great for customizing bottle sizes!
Remember, beyond the newborn stage, exclusively human milk fed babies will only EVER need about 4-6oz of milk per feeding.
Lipase and Frozen Milk: All human milk contains an enzyme called Lipase. Some humans naturally produce milk with higher levels of this enzyme than others, AND, levels can increase the longer that milk is left at room temperature or in the refrigerator before it is frozen. This can lead to a bit of a “soapy” taste for your baby when the milk is then warmed/thawed and offered to them. Some babies could not care less about this. However. Some REALLY do care. You should consider “testing” your frozen milk early on by offering it to your baby after about 1 week in the freezer, or at least WELL before the 8-month mark, so that you are not faced with a freezer full of milk that your baby is not interested in eating. If when you offer your thawed, “soapy” smelling milk to your baby and they are rejecting the bottle (if they’re rejecting and it does not smell soapy - reach out for a virtual consult and we’ll chat), you may need to consider scalding your milk before freezing, or decreasing the time at room temperature/refrigerator before freezing. Read more about this here.
What happens if I left the milk out for longer than 8-8-8? WE STILL DO NOT THROW IT AWAY. Get a separate freezer-friendly container, and start collecting “Bath Milk.” Unless the milk literally smells rancid, you should feel empowered to keep every drop, as it still has wonderful benefits for your baby’s skin barrier! Next time baby gets a rash, thaw some of the “Bath Milk” and toss it in baby’s bath.
Feeding expressed milk to your baby
Okay! You’re ready to offer your expressed milk to your baby. Now what? First, if your baby is younger than 3 weeks, you might consider holding off on bottles a bit longer, and choosing an alternative form of supplementation in order to protect your at-the-breast feeding relationship if that is a priority to you. Read more about this here! If your baby is ready for bottles, it’s VERY important to carefully consider the bottles and nipples you’ll use, as well as bottle feeding technique, and how they may impact the sustainability of your at-the-breast feeding relationship (Stay tuned for a post on bottle/nipple choice and feeding techniques). The remainder of this post will simply be addressing safety guidelines for offering expressed milk to your baby.
Offering Milk from Room Temperature or the Fridge
First, consider whether you actually need to reheat your milk. If your baby is above their birth weight and continuing to gain weight along their growth curve, it might be a good idea to switch up the temperature of milk you offer to your baby to let them know that it is in fact JUST FINE to drink cold or room temperature milk ;) This way, you can be less concerned about finding warm water or other heating options when you’re out of the house! Work smarter, not harder, friends!
If your milk fat has separated in storage, do not shake it to recombine! Simply warm the bag/bottle by using the techniques below, or by gently rolling/warming it in your hand for a few minutes until the fat reconstitutes into the rest of the milk.
Babies who need a bit more weight gain support (or who have caregivers with plenty of time and energy to concern themselves with milk temperature) should drink milk at body temperature, about 98.6 degrees Fahrenheit. Unless you are scalding your milk for Lipase-related reasons (see above), try your hardest to never heat human milk higher than body temperature. That said, if you do, WE STILL DO NOT THROW IT AWAY. It might have slightly less nutritional value than if it had not been heated that high, but as long as you let it cool back down to body temperature, it is perfectly safe to offer to your baby, or to save for bath milk if you have an oversupply.
There are PLENTY of fancy bottle warmers out there y’all. In the interest of your wallet, counter space, and the environment, I say skip them. My recommendation instead is a groundbreaking technique called… a mug and warm water. Simply place your bottle under warm running water until holding and rotating the jar or bottle in your hand feels like… the same temperature as your hand :) I do not recommend reheating milk in plastic bags; reconstitute fat with your hands, then transfer milk to bottle before heating.
If you’re using Dr. Brown’s bottles, you should not reheat milk in the bottle with all the green parts in place - this can lead to a leaky mess! Just reheat with the lid and nipple on, and then put the green parts in after the bottle is warmed.
NEVER microwave milk (or water for formula). This can lead to “hot spots” in the milk that can injure your baby, and it can degrade the nutritional value of your milk.
Once you have offered the bottle to your baby, as in they have latched and taken sips from the bottle, that milk is now on a new timeclock. There is a natural and expected exchange of bacteria from your baby’s mouth, back into the bottle when they are eating. You will see recommendations to use or toss that milk within 1-2 hours… I recommend just planning to use it by the end of the day.
Be careful with “saving the leftovers” for the next feeding - some parents get into the trap of saving an ounce or so from an initial feeding, then adding more milk to that bottle for the next feeding, which baby then also does not finish. Remember, the bacteria timeclock started from the INITIAL feeding, and any milk added to that bottle is on that same clock. I recommend instead that you offer the leftover ounce or so in the initial bottle first, and simply have a separate bottle prepped in case baby is hungry for more after that.
It IS okay to put leftover milk in the bottle back in the fridge, but also fine to leave on the counter, assuming you will offer it to baby within the next 4-6 hours.
Thawing Milk from the Freezer
Be sure to use your oldest frozen milk first!
You can thaw human milk in a couple different ways:
Leave bag/bottle in the refrigerator overnight to slowly thaw (safest but slowest way), and then choose whether or not to heat to body temperature
Warm water and mug (quicker)
Bottle warmer (quickest)
Once milk has been fully thawed (no more ice crystals are present), it must be used or saved for Bath Milk within 24 hours. Consider labelling the bag/jar/bottle with the time that it was fully thawed if you are putting it in the fridge. NEVER refreeze human milk with the intention to feed to baby.
Once you have offered the thawed milk bottle to your baby, as in they have latched and taken sips from the bottle, that milk is now on a new and SHORTER timeclock than if the milk was room temperature or refrigerated. We must assume that thawed milk has a bit less bacteria-fighting power due to it being reheated. Therefore, milk that is leftover in the bottle should be used in the very next feeding, within 2-4 hours, or saved for bath milk. Again, be mindful of adding milk to that bottle for the next feeding; consider starting the feeding with two bottles prepped.
If you have any questions at all, please leave them in the comments below and I would be thrilled to answer them for you, or direct you to a resource who can serve you better!
FAQs:
Should I be concerned about offering milk to my baby that was pumped at a certain time of day?
Short answer: NO. If you have an absolute excess of time and energy to be concerned about this, sure it would be great to offer morning/daytime milk to your baby in the morning/daytime, and the same for nighttime! There are certain hormones and fat level changes that do occur throughout a 24-hour period in human milk production. AND. Doing or not doing this will not be lifechanging. I promise.
Should I be concerned about offering milk to my baby that was produced when they were much younger than they are now?
Short answer: NO. While there are indeed nutritional content changes that occur in your milk as your baby gets bigger, and this is why if your baby were to eat exclusively freshly expressed milk they would never need more than about 4-6 ounces per feeding despite their increased need for calories (aren’t our bodies incredible?), you really really really should not concern yourself with this. Your baby might need more volume of milk if they are older and you are offering milk from when they were much younger. Again if you have an excess of time and energy, you could consider tapping into your frozen stash a little bit more frequently in those early months to keep a bit more of an aligned timeline. This is NO big deal. I promise!