Breastmilk and formula: Preparation and storage guidelines

Whether you decide to breastfeed, pump or formula feed, you will need to know the storage and preparation guidelines for breastmilk and formula to make sure it is safe for your baby.

A woman checking the temperature of a bottle of milk on her wrist.

You should always test the milk or formula temperature before feeding your baby.

Marshfield Clinic Health System has international board certified lactation consultants, pediatricians and registered nurses available to help families with breastfeeding, formula feeding and other related questions after birth in the hospital and beyond.

When feeding your baby breastmilk or formula, you always want to clean your hands and the work surface before and after preparation.

Wash your hands thoroughly with soap and water.
Clean the bottles in a dishwasher with hot water and a heated drying cycle (sanitize cycle), or scrub bottles in hot, soapy water and then sterilize them. (Place bottles in boiling water for five minutes to sterilize).

Breastmilk storage and preparation guidelines

American Academy of Pediatrics recommends exclusive breastfeeding or breastmilk feeding for the first six months of your baby’s life. If you express or pump breastmilk, you can store in the refrigerator for up to four days. After four days, you can freeze your breastmilk for six to 12 months, depending on the type of freezer.

“Breastmilk may be stored for up to 12 months in a chest freezer where temperatures are colder,” said Jessie Richardson, lactation consultant with Marshfield Clinic Health System.

Freshly expressed breastmilk may be kept at room temperature for up to four hours before feeding. Any leftover breastmilk after a feeding should be thrown out after two hours.

Once you thaw your breastmilk from the freezer, Richardson says you should use it within 24 hours to be safe for your baby.

“Do not microwave breastmilk,” she said. “Thaw milk in a refrigerator overnight or place in warm water. Swirl in the bottle or bag to mix.”

Watch video on guidelines for breastmilk storage.

How to prepare for formula feeding

If your baby is fed formula, the Center for Disease Control (CDC) and World Health Organization recommend that you choose infant formula sold in liquid form, especially when your baby is younger than 3 months of age.

“Liquid formulas are made to be sterile, whereas powdered formula, in rare cases, can be contaminated with bacteria that can be harmful to your baby,” Richardson said.

Powdered infant formula

Prior to 3 months of age, if using powdered infant formula, follow these steps to make sure the formula is as safe as possible to feed to your baby:

Keep powdered formula lids and scoops clean, be careful not to touch them and be careful with what they touch.
Close the containers of infant formula or bottled water as soon as possible.
It is recommended to heat the water to 158°F when making formula, even if bottled water is used. To ensure the water is heated appropriately, boil the water to be used at least two minutes.
Carefully follow the mixing instructions on the formula packaging to add formula to heated water.
Gently shake, rather than stir, formula in the bottle.
Water should not be allowed to cool for more than 30 minutes. Check the formula to ensure it is not too hot before feeding your baby:
- Run the prepared, capped bottle under cool water or place it into an ice bath, taking care to keep the cooling water from getting into the bottle or on the nipple.
- Check the liquid temperature before feeding to avoid scalding the baby’s mouth.

“If you have well water, it is important to have it tested prior to using for formula preparation,” Richardson said. “Contact your health department for assistance with this. If your well water has not been tested, use bottled water until this is completed. Follow the above steps using bottled water to prepare formula safely.”

Liquid concentrate infant formula

If using liquid concentrate infant formula, it should be mixed with water that has been boiled. This ensures that the water used for mixing is not contaminated with bacteria.

“When in doubt, throw it out,” Richardson said. “If you cannot remember how long you have kept formula in the refrigerator, it is safer to throw it out than to feed it to your baby.”

Watch video on formula preparation guidelines.

Formula storage guidelines

When using ready-to-feed liquid infant formula, you should feed within two hours of opening.

Leftover formula, in an infant bottle that baby has eaten out of, should be discarded. Once opened, ready-to-feed formula can be safely kept in the refrigerator for up to 24 hours. Follow specific guidelines recommended by the formula company on the packaging.

Once a container of infant formula is opened, store in a cool, dry place with the lid tightly closed. Do not store it in the fridge.

“Most infant formulas can be used within one month of opening the container, but check the label or write the date on the lid to help you remember,” Richardson said. “never use formula after the “use by” date on the container.”

Here is a simple chart for breastmilk and formula storage for healthy, full-term infants.