How to Collect, Store, and Prepare Breast Milk

How to Collect, Store, and Prepare Breast Milk

breastfeedingUpdated July 7, 2023

by Nina Spears

The Baby Chick®: Pregnancy, Birth & Postpartum Expert


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Almost every breastfeeding mother has a time when they need to pump, store, and prepare breast milk for their baby. For example, if you have to go back to work and want to continue breastfeeding, if you want your partner to help with a feeding, or if you have to run errands. It’s any time you must be away from your little one for several hours. This is why pumping your breast milk can be very convenient and sometimes necessary.

As a postpartum doula, many clients I have helped have often needed advice and assistance on how to pump and store, and sometimes preparing the breast milk isn’t done correctly. I wanted to share some tips below to answer questions about correctly storing and preparing your breast milk. Hopefully, these tips will make this process a lot easier!

How to Collect Breast Milk

  • The first thing that you should do is wash your hands with soap and water.
  • Then, ensure you have washed the bottles and breast pump parts in hot, soapy water. Some people boil water and place the pump parts and bottles to sterilize. Others use their dishwasher since the temperature it reaches also helps to sterilize. Just make sure that the rest of the dishes are pre-rinsed. You don’t want leftovers on them—tips for properly cleaning a breast pumpNOTE: Do NOT wash the tubing in a dishwasher or sterilize it in any machine. This can cause water to get into the tubing. This isn’t good because water can get into the machine and break it.
  • You want the parts to air dry, so lay them 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, and follow the suggestions. You can also watch YouTube videos to ensure you assemble and use the pump and parts correctly.
  • You do not have to sterilize your pump parts every use. Between using them, you can hand wash with soapy hot water. The CDC recommends you sterilize the pieces once a day.1
  • When you are ready to start pumping, ensure you have the correct size breast shields so your nipple fits comfortably. The standard kit that most families purchase only comes with one size shield. However, there are different shields available that you can buy separately. Most of my clients experience that the shield it comes with is too small. Make sure to check if you need to purchase a larger size. Medela makes breast shields to fit all nipple sizes, from small to extra large.
  • Lactation consultants recommend not introducing a bottle until breastfeeding has been established and is going well. I’ve heard many times from different lactation consultants to introduce a bottle. Some said three to four weeks, while others said longer than six weeks. I usually recommend starting slowly and introducing one bottle at two to three weeks. From there, you can slowly build up. 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 it too soon and for too many feedings.
  • If returning to work, you will want to begin pumping to store milk one to two weeks before you return. Many working moms use the fresh milk they pump while at work for feedings the next day. They bring home the 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 breast milk for emergencies.

How to Store Breast Milk


  • It is normal for pumped milk to vary in color, consistency, and scent depending on your diet. When you pump your milk and let it sit for a little while, it 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 breast milk. You can add small amounts of cooled breast milk to the same refrigerated container throughout the day. But you do not want to add warm milk to already cooled milk.
  • To store, pour your milk into breast milk collection bottles or disposable bags designed specifically for breast milk. The bottle must be a clean, capped glass or hard plastic, BPA-free container.
  • Breast milk storage bags might tear, leak, and contaminate more easily than hard-sided containers. Place the bags in a hard plastic food storage container with a tightly sealed lid for extra protection. Even though disposable bags are made for breast milk, these things still happen. I have seen several mothers cry over their spilled milk, so carefully store it.
  • To easily find the oldest bag of stored breast milk, check out Milkies’ The Freeze.
How to Collect, Store, and Prepare Breast Milk
  • Again, seal containers tightly to prevent any leaking. 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.
  • Place the containers in the back of the refrigerator or freezer, where the temperature is the coolest.2 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 breast milk 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. Many 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, leave some extra room at the top of the container or bag. This is because the liquid will expand when frozen. You don’t want the bottle or bag to burst.
  • Breast milk storage chart to learn how to store breast milk:
breastmilk storage guidelines

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

How to Prepare Breast Milk

How to Collect, Store, and Prepare Breast Milk
  • 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 breast milk has been stored in your fridge, you can either use a bottle warmer or place it under running hot water in a cup or bowl full of hot water to warm the bag or bottle. Do NOT microwave your breast milk or heat it quickly on the stove. This also damages the composition of the milk and can create hot spots that can scald your baby’s mouth. No fun.
  • If you’re trying to thaw your frozen breast milk, first move your milk to your fridge the night before. You can hold the bag or bottle under warm running water if you need it sooner. It will take longer to thaw and warm than a cool/cold bag of breast milk stored in the fridge. When you have a hungry baby, that might not be ideal.
  • Another major question I get asked is if you can refreeze your breast milk. No, you can’t. Do NOT refreeze. Once it’s frozen and thawed, you must use it within 24 hours (which is how long it is safe in the refrigerator.)3

So there it is! My advice on properly collecting, storing, and preparing your breast milk. I hope it helps!

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