Formula Feeding FAQs: Preparation and Storage

The major health organizations — including the American Academy of Pediatrics (AAP), American Medical Association (AMA), the American Dietetic Association (ADA), and the World Health Organization (WHO) — agree that breast milk is the ideal form of nutrition for babies (especially during the first 6 months). However, only you can decide what's best for you and your baby.

Whether you've decided to formula feed your baby from the start, are supplementing your breast milk with formula, or are switching from breast milk to formula, you're bound to have questions. Here are answers to some common questions about formula feeding.

Do I need to sterilize my baby's bottles?

Yes. Before the first use, you'll need to sterilize nipples and bottles in a rolling boil for 5 minutes. You can also sterilize them with a store-bought countertop or microwaveable sterilizer, but boiling works just as well and costs nothing.

After that, you'll need to wash bottles and nipples in hot, soapy water (or run them through the dishwasher) after every use. They can transmit bacteria if not cleaned properly.

How do I prepare my baby's bottles?

Prepare your baby's formula by mixing water and the appropriate amount of powdered infant formula. The packaging on the side of the formula container will tell you how much to use. Carefully follow the directions. You can use tepid (room temperature) tap water, as long as your local or state health departments have labeled it as safe to drink.

If you're concerned about your water, you may sterilize it to kill germs. Here's how:

pour cold tap water into a teapot or saucepan
place pot on the stove over medium heat
bring water to a rolling boil, and let boil for about a minute
let the water cool until it's at room temperature

Test to see if the water is cool enough for your baby to drink by shaking a few drops of water on the inside of your wrist. If it stings, it's still too hot. Once water has cooled, don't let it sit longer than 30 minutes before adding it to the formula.

Once prepared, the formula is ready to feed to your baby immediately without additional refrigeration or warming. Formula that's been prepared should be consumed or stored in the refrigerator within 1 hour. If it has been at room temperature for more than 1 hour, throw it away. And if your baby doesn't drink all the formula in the bottle, throw away the unused portion — do not save it for later.

Formula may be prepared ahead of time (for up to 24 hours) if you store it in the refrigerator to prevent the formation of bacteria. Open containers of ready-made formula, concentrated formula, and formula prepared from concentrate also can be stored safely in the refrigerator for up to 48 hours.

How do I warm my baby's bottles?

Some babies may actually prefer cold or room-temperature bottles to warm, especially if you start serving them that way from the get-go (which can make things easier for you in the long run).

But if your baby does prefer a warm bottle, remember that the microwave can create dangerous "hot spots" in bottles, so you should never microwave formula.

Instead, you can:

Run the bottle under very warm or hot water for a few minutes.
Put your baby's bottles in a pan of hot water. Just be sure to remove the pan from the heat source before placing the bottle in it.
Use bottle warmers that either sit on your countertop at home or plug into your car's lighter.

Whichever way you choose to heat your baby's bottles, be sure to shake the bottle vigorously. Then test the temperature of the formula by squirting a drop or two on the inside or your wrist before feeding your baby. It should be lukewarm (barely warm) not hot.

How long can mixed formula keep in the fridge?

You should always refrigerate any bottles you fill for later feedings to prevent bacteria from growing, as well as any open containers of ready-to-feed or concentrate formula. Throw away any mixed formula after 24 hours and any open ready-to-feed or concentrate formula after 48 hours.

How long can a bottle keep at room temperature?

Discard any prepared or ready-to-feed formula that's been sitting out after 1 hour.

If formula is left over, can I offer it again?

No, throw away any leftover formula. There's a chance bacteria may have formed since the last feeding, which could make your baby sick.

Reviewed by: Joseph DiSanto, MD, and Karin Y. DiSanto, IBCLC
Date reviewed: February 2012

Related Resources

U.S. Food and Drug Administration (FDA) The FDA is responsible for protecting the public health by ensuring the safety, efficacy, and security of human and veterinary drugs, biological products, medical devices, our nation's food supply, cosmetics, and products that emit radiation.

American Dietetic Association The American Dietetic Association offers nutrition news, tips, resources for consumers and dietitians, and a find-a-nutritionist search tool.

Women, Infants, and Children (WIC) The Special Supplemental Nutrition Program for Women, Infants, and Children - better known as the WIC Program - serves to safeguard the health of low-income women, infants, & children up to age 5 who are at nutritional risk by providing nutritious foods to supplement diets, information on healthy eating, and referrals to health care.

American Academy of Pediatrics (AAP) The AAP is committed to the health and well-being of infants, adolescents, and young adults. The website offers news articles and tips on health for families.

American Academy of Family Physicians This site, operated by the American Academy of Family Physicians (AAFP), provides information on family physicians and health care, a directory of family physicians, and resources on health conditions.

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