Heating Human Milk

Image copyright Lisa Olschewske Photography, used with permission.

Heating Human Milk in the Microwave

When baby is hungry and human milk needs to be warmed quickly, many caregivers or parents are tempted to warm it in the microwave oven. This speeds the process so that the feeding can proceed more quickly. However…

Warming milk in the microwave is never recommended.

There are two main reasons to avoid this practice.

  1. No liquid or food being fed to any infant should be warmed in a microwave. Milk heats unevenly in a microwave, and can create hot spots that could burn your baby’s mouth. The American Academy of Pediatrics states that uneven heating can scald your baby. The CDC makes the same recommendation. Bottles could explode if heated too long. Controlling the temperature in a microwave is very difficult.
  2. Human milk is a living fluid. Microwaving breast milk can destroy valuable immunological components. Microwaving at high temperatures causes a marked decrease in anti-infective properties. Overheating during the warming process causes denaturation and inactivation of milk’s bioactive proteins and decreases fat content.
What is the best way to thaw my milk?

Milk can be thawed several ways. Slow, gentle thawing is best to protect and preserve the healthy qualities of the milk. One excellent way is to allow it to thaw overnight in the refrigerator. This method preserves the most fat content of the milk. Another is to warm some water, remove it from the burner or microwave and set the bottle in the warm water to thaw. Be sure the heated water is warm, not hot. Human milk can also be thawed by rotating the container under running warm water. Some caregivers thaw human milk in a waterless bottle warmer. Once thawed, it should be used within 24 hours.

How can human milk best be warmed?

Refrigerated human milk is best heated by holding the container of milk under cool running water and gradually adding warmer water until the milk is warmed to room temperature. If running water is not available, a pan of water can be heated on the stove. The container of milk can be placed in the warm water once it has been removed from the heat source. Once heated, it should be gently shaken to even out the temperature and mix the fat particles into the milk. Test a drop of milk on the top of your hand before feeding. It should feel lukewarm.

Even though the use of the microwave for warming human milk is tempting, it is not wise. Please advise caregivers in daycare settings to remember these precautions when preparing your milk for your little one.