How to Properly Collect, Store & Prepare Breastmilk

How to Properly Collect, Store & Prepare Breastmilk | Baby Chick

How to Properly Collect, Store & Prepare Breastmilk

Almost every breastfeeding mother has a time when they need to pump, store, and prepare their breastmilk for their baby. If you have to go back to work and want to continue breastfeeding, if you want your partner to help or have to run errands, or any time you have to be away from your little one for several hours at a time, pumping your breastmilk can be very convenient and at times necessary. As a postpartum doula, a lot of my clients that I have helped have often needed advice and assistance on how to properly pump and store, and sometimes preparing the breastmilk isn’t done properly. I wanted to share some tips below to answer any questions that you may have about properly storing and preparing your breastmilk. Hopefully these tips will make this process a lot easier!

Collecting Breastmilk

  • The first thing that you should do is wash your hands with soap and water.
  • Then, make sure that you have washed the bottles and breastpump parts in hot, soapy water. Some people boil water and place the pump parts and bottles to sterilize and others use their dishwasher since the temperature it reaches also helps sterilize as well. Just make sure that the rest of the dishes are pre-rinsed. You don’t want leftovers on them.
    • NOTE: Do NOT wash the tubing in a dishwasher or sterilize in any machine. This can cause water to get into the tubing which can cause water to get into the machine and have it break.
  • You want the parts to air dry so you can lay them out on a clean towel or paper towel. You can also use a drying rack.
  • If you are unsure how to use your pump, read the instructions in the book that comes with your pump and follow the suggestions.  You can also watch some YouTube videos to make sure that you’re assembling and using the pump and parts properly.
  • I like to let people know that you do not have to sterilize your pump parts every time after you use them. It’s recommended that you sterilize the parts once a day but between using them, you can hand wash with soapy hot water.
  • When you are ready to start pumping, be sure that you have the right size breastshields so that your nipple fits comfortably.  The standard kit that most families purchase usually only comes with one size shields but there are different shields available that you can buy separately. Most of my clients experience that the shield it comes with is too small so check if you need to purchase a larger size. Medela makes different size breastshields to fit all nipple sizes, from small to extra large.
  • Lactation consultants recommend that you don’t start introducing a bottle until breastfeeding has been established and is going well. I’ve heard from different lactation consultants many different times to introduce a bottle. Some have said three to four weeks and others have said longer than six weeks. I usually recommend to start of slow and introduce one bottle at two to three weeks and slowly build up from there. I’ve seen many babies only want the boob because their parents never introduced the bottle until later and I have had other babies only want the bottle because they introduced the bottle too soon and for too many feedings.
  • If you are returning to work, you will want to begin pumping to store milk one to two weeks before you return. A lot of working moms use the fresh milk they pump at work for feedings the next day. They bring home that fresh milk and refrigerate it for the next day’s feedings. So Friday’s milk is used for Monday. You want to save your frozen milk for emergencies.


Storing Breastmilk

  • I want you to know that it is normal for pumped milk to vary in color, consistency and scent depending on your diet. When you pump your milk, you will notice when it’s sitting for a little while that your milk will separate into layers. The cream will rise to the top and be a lighter color.
  • A lot of people wonder if they can combine breastmilk together. You can continue to add small amounts of cooled breastmilk to the same refrigerated container throughout the day, but you don’t want to add warm milk to already cooled milk.
  • For storing, pour your milk in breastmilk collection bottles or in disposable bags specifically designed for breastmilk. The bottle must be a clean, capped glass or hard plastic, BPA-free container. Warning: Breastmilk storage bags might tear, leak and become contaminated more easily than hard-sided containers. For extra protection, place the bags in a hard plastic food storage container with a tightly sealed lid. Even though the disposable bags are made for breastmilk, these things still happen. I have definitely seen several mothers cry over their spilt milk so make sure that you store it carefully.
  • To easily find the oldest bag of stored breastmilk, check out Milkies’ The Freeze or Dr. Brown’s Storage Tray.



  • Again, seal containers tightly to prevent any leaking and write the date and time on a piece of tape on the bag or bottle. This way you will know which is the oldest since you want to use the oldest milk first.
  • You also want to place the containers in the back of the refrigerator or freezer, where the temperature is the coolest. If you don’t have access to a fridge or freezer, store the milk temporarily in an insulated cooler.
  • I recommend that you freeze your breastmilk in two to five ounce portions. Small amounts thaw faster so you will waste less milk this way, save more time, and will avoid over-feeding your baby. A lot of parents want their babies to finish the whole bottle since they don’t want to waste a drop, but you do not want to overfeed your baby. Also, be sure to leave some extra room at the top of the container or bag since the liquid will expand when frozen. You don’t want the bottle or bag to burst.
  • Read my Breastmilk Storage chart to learn how to store breastmilk.

If your baby was born premature, these guidelines may differ slightly.  You should check with your health care provider for the recommended storage guidelines for your specific situation.

Preparing Breastmilk

  • When you are ready to prepare the breast milk, you want to gently swirl the warmed bottle to mix the milk layers. Do NOT shake the milk. That damages the milk.
  • If your breastmilk has been in stored in your fridge, to warm the bag or bottle you can either use a bottle warmer or place it under running hot water, in a cup or bowl full of hot water. Do NOT microwave your breastmilk or heat quickly on the stove. This also damages the composition of the milk and can create hot spots which can scald your baby’s mouth. No fun.
  • If your trying to thaw your frozen breastmilk, first move your milk to your fridge the night before. If you need it sooner than that, you can hold the bag or bottle under warm running water. It will obviously take a longer to thaw and warm than a cool/cold bag of breastmilk that was stored in the fridge. When you have a hungry baby, that might not be ideal.
  • Another major question that I get asked is if you can refreeze your breastmilk. No, you can’t. Do NOT refreeze. Once it’s frozen and then thawed, you must use it within 24-hours (which that is how long it is safe in the refrigerator.)

So there it is! My advice on how to properly collect, store, and prepare your breastmilk. I hope it helps! 🙂


About the Author /

The Baby Chick® & CEO of Baby Chick®


  • Traicy
    September 4, 2015

    Very helpful, thanks! How long is breastmilk good for at room temperature, refrigerated, and frozen? I’m being tild different times for room temperature which is confusing…please help!

  • Aubrey
    September 5, 2015

    I recently read that shaking breast milk doesn’t damage it in anyway. Supposedly, this was just another rumor started by formula producers in an effort to discourage the efforts of breastfeeding. I’m not sure if the actual science behind it, so I’m curious if maybe you do? Thanks

  • angel
    September 6, 2015

    Hey I was wondering if I stored my breastmilk in the fridge and warmed it up then stored it back in the fridge an re warm if that was harmful or if its okay

  • Sharon
    September 7, 2015

    Hi I have a 2 months old baby I’m breastfeeding every 2-3 hours and he has three days he hasn’t gone poop.
    Is it norma???

  • Michaela
    September 7, 2015

    Hi Nina, during the first few weeks my baby and I developed thrush. do you suggest freezing that milk? Do it have the same freezer shelf life? Thanks in advance!

  • Rachel
    September 8, 2015

    What about if your breast milk contains excess lipase? I read that I’m supposed to bring it to just barely where it’s boiling then immediately freeze it. Does that harm it in some way? Any other solutions?

  • Sangeeta
    September 9, 2015

    Hi Nina

    Thank you for the information. A few questions:

    1.) I want to start string some bottles for full feedings, however I’m breastfeeding full time and not able to pump enough in one go. Can I add freshly expressed milk to a bottle in the fridge from a pumping session earlier in the day? I usually can pump about an ounce at each session so wondering if I can start to change mine the expressed milk from the different sessions?

    2.) are there any good labeling solutions you would recommend?


  • Amy
    September 14, 2015

    Hi Nina,
    I had two problems when I was breastfeeding;
    1) I tried to feed my son so breastmilk that I thawed from the freezer and he rejected it so I tasted it and it was sour and awful tasting. I tried multiple tastes from the storage bag and threw out almost 30 bags of stored breastmilk. I was so upset. My only thought was that perhaps the freezer was not cold enough. Thoughts?

    2) At about 4 months I noticed my milk supply was low. Lactation cookies and Fenugreek did nothing for me. In retrospect I wonder if I should have started pumping sooner than 6 weeks after my son was born. I did not pump as much because I was feeding on demand and was worried I wasn’t going to have enough milk for when my son wanted it and I just wanted to be “tied down” to the pump (having down time from baby duties was necessary). I am aware of the more stimulation there is the more milk you produce. I work in the medical field so pumping between patients is stressful when you don’t have much down time so this enivironment may not have been suitable for pumping.

    Please help!

    Thanks, Amy

  • stephanie
    September 15, 2015

    Hi. Great info, thank you for posting! My question is: my husband gives our 3m baby girl a dream feed at 11pm. Sometimes she dies not finish the bottle of 4oz. Most nights she does. For those nights that she doesn’t, is it ok to put that bottle in the fridge and give it to her in the morning, between 4-6am? (Not re- heating

  • Sara
    October 3, 2015

    Hi there my little lady is 3 months old on monday… About two weeks ago i finally broke down and purchased a chest deep freezer as our refrigerator freezer was chucked full of frozen milk… My question is after transferring the milk i ha already froze in our refrigerator freezer to the deep freeze is this milk now good for a yr? Or do i need to use it up within the 3-4 months guidelines for the refrigerator freezer? Thank you!!!

  • Lynn
    October 4, 2015

    Hello! I am a first time mom to a 4 day old. Thank you for all the wonderful information. We are having a hard time having her latch on so I started pumping from day 1. I am still trying to breastfeed her before giving her the bottle in hopes she will catch on. Any advice would be wonderful. I am also wondering how much milk to too much for a newborn. I’ve read so many different articles and amounts I’m just so confused. I want to make she she is getting enough milk but I also don’t want to under or over feed her.

    Thank you!!

  • Erica
    October 5, 2015

    Having are very hard time getting milk to come in. Had my daughter the 25th ( 10 days ago) and Im not producing milk like I should so had to give her formula. Now she is so used to the bottle she won’t Breast feed. When I pump I get 1/2 oz from both combined

  • Mercedes
    October 9, 2015


    I was wondering how long is the milk good for after I take it out of the fridge? I would like to start saving milk a day before, so that when my husband and I want to go out for the day I have milk to feed my baby. Instead of having to breastfeed while we are out all the time.

  • Samantha
    October 10, 2015

    Hi Nina. Thank you for all this wonderful information. My baby is 4 weeks old and we are trying to introduce a bottle but have been unsuccessful so far. I’m continuing to breastfeed and she’s doing really well, but I have to go back to work in two months. Do you have any tips on introducing a bottle to a breastfed baby? Thank you!

  • Alicia
    October 10, 2015

    Hi, I have a large supply of frozen breastmilk in a standing freezer. The temp is set at the mid range. Should I start giving my baby the thawed frozen milk to rotate the supply or should I keep giving her the fresh milk I pumped the day before? Thanks for your help.

  • Keri
    October 26, 2015

    Why is it not ok to mix milk that has been cooled with freshly pumped milk?

  • Sarah
    November 4, 2015

    Hi, I have a weird sort of question. I exclusively pump and have from the beginning. I heard that when babies breastfeed that the bacteria in their saliva can enter the breast telling it to create certain antibodies and nutrients to the milk and the properties of breastmilk changes as your baby ages. Will my baby lack nutrients since he hasn’t “technically” breastfed since we were both in the hospital last May?

  • Echo
    November 4, 2015

    Hi Nina, thank you for the info. I have been looking for clarity for a while and this article finally clears up my questions. I do have another question I have been trying with my son ( now 4 months), to take a pacifier and he refuses every time. It’s frustrating because I have become his pacifier. I try to introduce at different times and he just spits it out. Do you have any tips?

  • Janet
    November 5, 2015

    Hi Nina,

    I would like to know how long is the milk good if I feed my baby and she does not finish the entire 2oz? Do we apply the same rule as with formula (good for an hour) or should I discar it right away? Thanks.

  • Amber
    November 16, 2015

    Thanks for this great blog! My question is i know breastmilk lasts in the refrigerator a few days before going bad so i have a few bottles from this week i have pumped. My question is if i dont use the refrigerated bottled milk within the recommended 4 days if i put it in the freezer on the 4th day is that okay or should i immediatley freeze any milk i want to keep in the deep freeze?

  • Amanda
    November 21, 2015

    All your responses are so helpful! I have a question about combing expressed milk – if you combine milk from the same day different pump
    Sessions can this contribute to a foremilk/hind milk imbalance. I am just wondering bc some of my bottles don’t have much of the cream and some do. Also what happens if you combine milk from different days to create enough for a bottle? Just wondering why that’s a no.

  • Katie solis
    November 22, 2015

    My baby is 4 1/2 months old. I’m breast feeding but I do not produce enough to strictly breast feed. I only produce 1-2 oz each pumping. I don’t produce enough to fill him each nursing session. Iv been seeing a lactation consultant. But not much improvement. I’m doing everything I can. I got mastitis with my first born very badly and was hospitalized. So nursing is difficult for me to say the least. Any suggestions on how to build my supply? I have to pump two to three times to get one full bottle. It’s exhausting.

  • Janeal
    December 11, 2015

    Is it okay to feed your baby cold milk that you have stored in the fridge? I have fed my son bottles directly from the fridge without heating and he doesn’t seem to mind.

  • Daisy Perez
    December 14, 2015

    Hi I’m wondering how long does thawed milk stay good for? I’ve noticed that when I thaw it out a bit before I need it it looks different, it seems to have small clumps. Is that normal or do I need to thaw it out only right before I need it? I’ve started to do that because I was scared it was spoiled but it would be convenient to be able to thaw it a bit before hand.

  • Vaneza
    January 26, 2016

    Hello, is any one selling or know of someone who is selling their electric pump? I’m a single mother with low income that can’t afford a $300 dollar pump. My insurance didn’t want to cover it either…

  • manu
    April 13, 2016

    Hello, I am a mom of 3 month old baby, i saved my breast milk and freezed it properly in madella bags. I tried to use 2 months old milk, and seems its upsetting my baby’s stomah, please advise if I should use it and if any precautions i Should take.

  • Iris
    November 26, 2016

    Hi I was wondering if I need to throw away the left over expressed breast milk after the baby drank it from the bottle, or can I save it for next feeding? Thanks

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