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How to Start Pumping, Bottle Feeding, and Storing Breastmilk

Learn how to get started pumping breastmilk while you're at work and how to properly store your milk.

This information is part of Virtua’s Breastfeeding resources collection. Please see our Breastfeeding Support Resources page to view the entire series.

The most effective tool for expressing breastmilk during the workday is a good-quality electric breast pump. Contact a lactation consultant, WIC program, or public health department to learn where to buy or rent a good pump.

Electric pumps allow you to express milk from both breasts simultaneously, reducing pumping time. Most health insurance plans will cover the cost of a breast pump. Check with your insurance company for details.

Getting started with a breast pump

Start by pumping once a day to begin storing milk. Most women find that they can pump more milk in the morning because the supply tends to be greater at that time of day.

Pumping before feeding your baby helps you increase your volume, but your breastmilk may consist of more watery, lower-fat foremilk. If your baby’s ready to eat, you may need to wait until after the feeding to pump. Pumping after feeding your baby will give you milk with a higher fat content (hindmilk).

You also could try nursing your baby on one breast while pumping the other at the same time. The baby's suck will stimulate the hormones that enhance milk production and flow. This may increase the amount of milk you get from the other breast.

Pump for 10-15 minutes on one or both breasts, and store your breastmilk in the freezer. You’ll likely pump 1-3 ounces of breastmilk per breast at each session. However, the amount also depends on the pump you’re using and your body’s response to it. This amount may increase after a few days if you pump at the same time every day. When your nurse and pump, the increased stimulation will increase your milk production

Introducing your baby to bottle feeding

When you first start pumping, offer your baby a supplemental bottle of breastmilk about every third day that you pump.

Store that morning's pumped milk in the refrigerator instead of the freezer. Reheat the milk by placing the storage bag in a cup of warm water and offering it as a snack in a bottle around dinnertime. This gives you a chance to get out for a bit without skipping an entire feeding. Avoid giving a supplemental bottle through the night, as it can interfere with your milk supply.

Some babies are more willing to accept a supplemental bottle from someone other than their mom. However, each child is unique, so your baby may be happy to take it from you.

How to store breastmilk

Breast milk can be stored in clean glass or hard, BPA-free plastic bottles with tight-fitting lids. You also can use food-grade, plastic breastmilk storage bags to freeze your milk. However, using disposable bottle liners or other plastic bags to store breastmilk is unsafe.

Storing breastmilk after you pump

  • Write the date on the storage container. Include your child's name if you give the milk to a childcare provider.
  • Gently swirl the container to mix the breastmilk cream into the rest of the milk.
  • Refrigerate or chill your breastmilk right after you’ve pumped. You can put it in the refrigerator, place it in a cooler or insulated cooler pack, or freeze it in 2- to 4-ounce batches for later feedings.

Tips for freezing breastmilk

  • Wait to tighten bottle caps or lids until the milk is completely frozen.
  • Try to leave about an inch of space at the top of the container to allow it to expand while freezing.
  • Store milk in the back of the freezer—not on the freezer door.

Tips for thawing and warming breastmilk

  • Check the date on your breastmilk storage container. Make sure you use the oldest stored milk first.
  • You don’t have to warm breast milk, but you can take the chill off it and serve it at room temperature.
  • To thaw frozen milk, place it in the refrigerator overnight, run the bottle or bag of milk under warm running water, or set it in a container of warm water.
  • Never put a bottle or bag of breast milk in the microwave. Microwaving creates hot spots that could burn your baby and damage the components of the milk.
  • Swirl the milk and test the temperature by dropping some on your wrist. It should be comfortably warm.
  • It’s best to use thawed, room-temperature breastmilk within 1 to 2 hours, but it won’t harm your baby if used within 3 to 4 hours.
  • Use refrigerator-thawed breast milk within 24 hours. Don’t re-freeze thawed breast milk.
  • Wash your breast pump equipment every day with soap and water and let it air dry. This will help keep germs from getting into your milk.

Quick guide for storing fresh breastmilk


  • Temperature: Room temp (60°F-85°F)
  • Time: Up to Six to eight hours
  • Things to know: Containers should be sealed and kept cool. Throw out any leftover milk within one to two hours after feeding the baby.

Small cooler with an ice pack

  • Temperature: 59°F
  • Time: Up to 24 hours
  • Things to know: Keep ice packs in contact with milk containers at all times and limit opening the cooler bag.


  • Temperature: 39°F or colder
  • Time: Five to seven days
  • Things to know: Store milk in the back of the refrigerator, where it’s coldest.


  • Temperature: 24°F or colder
  • Time: Six months is best, but up to 12 months is okay if milk is stored at 0°F or colder.
  • Things to know: Store milk in the back of the freezer, where the temperature is coldest and most constant. Milk stored at 0°F or colder is safe for longer durations, but the milk quality could decrease.