Is It Safe to Reuse Breast Milk?

Reviewed by Dan Brennan, MD on March 02, 2021

Many mothers choose to breastfeed their infants after birth. They often pump milk to provide bottles for other family members to feed their baby. 

Can you reuse breast milk once you make a bottle? This depends on when the breast milk was expressed, or pumped, and if it was stored in the fridge or not.

About Expressed Breast Milk

Guidelines for Storing Breast Milk. Once breast milk is expressed, there are guidelines for how long the milk may be safely consumed. Generally speaking, breast milk is good for:

  • 4 hours when freshly expressed
  • 4 days in the back of your refrigerator
  • 6 to 12 months in a deep freezer

Of course, consider the environmental or other factors if you are wondering whether to feed your baby expressed breast milk that’s been left at room temp for an hour without refrigerating, or was in the fridge for a few days before freezing. If you’re concerned that breast milk is bad, smell it. As long as it doesn’t have a foul odor, it’s probably safe for your baby to drink.

Keep in mind that the fat in breast milk separates over time. This creates a congealed layer near the top of the bottle. This is completely normal. It’s not something you see in store-bought milk, because that milk has been pasteurized. Gently shake your bottles to mix the fat back in before feeding. The separation of milk fat is not a sign that your breast milk has gone bad.

Guidelines for Offering Breast Milk. Breast milk does not have to be warmed to give to your baby. It can be offered cold or at room temperature. Your baby may prefer warm breast milk, because the temperature of milk from your breast is warmer. Try to start out by feeding your infant bottles that are closer to room temperature to see if she minds.

If your baby prefers warm milk, purchase a bottle warmer instead of using boiling water or a microwave to heat it up. Bottle warmers are safer. They are specifically designed for warming a baby’s milk and provide a more consistent temperature.

Test the warmth of your child’s milk on the back of your hand before offering the bottle to your baby. If it feels too warm on your wrist, it could burn their mouth.

Use breast milk within 24 hours of thawing it from the freezer. Once you’ve taken breast milk out of the fridge and either warmed it up or allowed it to come to room temperature, it should be used within 2 hours. It is not safe to reuse breast milk that has been left out longer than 2 hours. Dispose of it if this is the case. Breast milk should never be re-refrigerated or re-frozen.

These guidelines are important. Bacteria can begin to grow in your breast milk if it is left out too long. Babies are much more sensitive to the dangers posed by bacteria, because their immune systems haven’t yet had the chance to build up antibodies used to fight off illness and infection.

Other Considerations for Giving Breast Milk Bottles

Opportunity to Bond with Baby. There is a misconception that you cannot bond with your baby as well when offering bottles instead of milk directly from your breast. This is not true. Hold your baby close when you give bottles and make eye contact while feeding. Talk to them with a soft voice as another way to enhance the bonding experience of feeding.

Offering breast milk in bottles allows everyone in your family an opportunity to establish a connection with your baby. Encourage the father, siblings, and grandparents to hold and feed your baby with expressed breast milk in bottles.

Your baby will feel more closely connected with each member of your family. This will ease the pains associated with your absence if and when you return to work.

Diapers. The poop of a breastfed infant is usually yellow and seedy. It will be softer than if your baby was formula-fed. Formula creates a darker, firmer stool. Some breastfed infants poop multiple times each day. It is not uncommon for a breastfed baby to go 7 to 10 days without a dirty diaper.

Show Sources


CDC: “Proper Storage and Preparation of Breast Milk.”

OFFICE ON WOMEN’S HEALTH: “Pumping and storing breastmilk.”

what to expect: “Formula-feeding your baby,” “Newborn and Baby Poop.”

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