Health Library

Collection, Storage and Use of Expressed Human Milk for Well Infants

Safe collection, storage and use of your expressed milk is important for the health of your child. These guidelines and tips will help you maximize the nutrients in your stored milk.

• Wash your hands before pumping. If soap and water are not available, use an alcohol-based hand sanitizer that contains at least 60% alcohol.
• Make sure you use a clean, dry collection kit. Follow the instructions that came with your pump for cleaning pump parts between each use, as well as how often to sterilize them.
• Sit comfortably. Think about or look at a picture/video of your child. Relaxation techniques that calm your body and mind can help increase the amount of milk removed from the breast.
• You may apply a warm, wet cloth for a few minutes before pumping to help milk release from the breast. A warm wet diaper works well to retain the warmth.
• You may gently massage the breast before and during pumping.
• Check to make sure the flange (the piece that fits over the breast and nipple) is the correct size when pumping milk.
• You should have no pain and be able to empty your breasts in a reasonable amount of time.
• Your nipple should not appear tightly squeezed when the pump is on.
• The wrong flange size can lead to decreased milk production and nipple pain and damage with continued use.
• The right size may change over time as your breasts and milk supply change.
• Some moms need a different size for each breast.
• If your pump has a vacuum strength control, it should be as high as it can be while remaining comfortable. This may be a little different each time you pump.
• Pumping usually takes 10 to 20 minutes per side for a single pump. Double collection kits will decrease the amount of time needed for pumping to about 15 minutes total.

Tips for Storing/Transporting Your Milk

• Hand-expressed or pumped milk may be stored in standard baby bottles (glass or plastic), other food-grade containers with tight fitting lids, or special bags for human milk storage.
• Do not use other plastic bags not meant for human milk storage, including baby bottle liner bags.
• Squeeze air from the top of bags before sealing and place bags upright to prevent leaking.
• Label each collection container with the date the milk was pumped.
• If you collect more than one bottle full of milk from one breast, mix the contents of both containers and swirl gently before dividing and placing in the refrigerator or freezer.
• This may indicate an oversupply of your milk.
• Please see our topic "Breast Milk Oversupply” for more information.
• Leave at least an inch at the top since milk will expand during freezing.
• You may combine milk from two different pumping times if needed. Allow the milk you just pumped to cool to the same temperature as the previously stored milk before combining.
• Store only 4 ounces per container so you don’t waste milk by having to thaw more than you need. Storing in smaller amounts is okay, too.
• When transporting milk, place it in an insulated bag or cooler with a frozen cold pack. Use, refrigerate or freeze the milk at your destination.

Human Milk Storage Guidelines for Well Children

Fresh human milk has the most active anti-infective properties, followed by refrigerated, and then frozen milk. When you use frozen or refrigerated milk, use the oldest first. When using thawed milk, it is best to also give your child fresh or refrigerated milk that day.

• Fresh milk at room temperature: Up to four hours at 77°F (25°C) or cooler. The milk can be moved into the refrigerator or freezer if not used within this time and your child did not put their mouth on the bottle.
• Fresh milk refrigerated at 40°F (4°C): Up to four days. The milk can be moved into the freezer if not used within this time. Store near the back of the refrigerator or freezer for best quality, not in the door.
• Fresh milk in cooler with frozen cold packs: No longer than 24 hours.
• Fully thawed milk in refrigerator: Up to one day (24 hours).
• Frozen milk in the freezer section of a refrigerator with its own outer door, at 0°F (-18°C) or colder: Within six months is best; up to 12 months is acceptable. Store near the back of the freezer for best quality, not in the door.
• Milk left in bottle after infant has finished feeding: Use within two hours and do not store for later use. If your milk is mixed with formula in the same bottle, discard after one hour.

Handling and Use of Your Expressed Milk

• Wash your hands before handling milk. If soap and water are not available, use an alcohol-based hand sanitizer that contains at least 60% alcohol.
• Milk should never be warmed or thawed in the microwave. The microwave can create hot spots in the milk. Microwaving or heating milk in very hot water may also decrease the anti-infective properties of human milk.
• Some babies prefer warm milk, but some do not mind cold or cool milk.
• Milk naturally separates during storage, and the cream (fat) rises to the top. Gently swirl the bottle of milk to mix it; avoid vigorous shaking.

Thawing frozen milk:

• Thaw your milk by placing the collection container in the refrigerator overnight, place in warm or lukewarm (not hot) water, or run under lukewarm water.
• Do not refreeze milk once it has been fully thawed.

Warming milk:

• Hold the container of milk under lukewarm running water.
• You may also place it in a container of warm or lukewarm water.
• Water should not touch the bottle lid or top of the bag.
• A bottle warmer can be used.
• Always check the temperature of the milk on the inside of your wrist before giving it to your child.

Contact Us

For additional information on this topic, call the Center for Breastfeeding Medicine at 513-636-2326.