Measuring and Mixing Formula

Medically Reviewed by Hansa D. Bhargava, MD on January 17, 2014
3 min read

No matter which type of formula you choose, it's important to measure and mix it properly so your baby safely gets the nutrition they need.

"Measuring and reconstituting infant formula is particularly important when it concerns low-birth-weight and premature babies," says David Saltzman, MD, a Chicago-area pediatrician. A baby with an immature system may have trouble digesting formula that's not prepared correctly, he says.

Mixing formula with too much water is particularly risky. "If you dilute the formula with more water, it will contain fewer calories per ounce and not provide enough calories for your baby to thrive," says Dyan Hes, MD, of Gramercy Pediatrics in New York. It can even lead to seizures and brain damage.

How to prepare formula depends on which type of formula you choose:

  • Powder
  • Liquid concentrate
  • Ready-to-feed

Powder. Most manufacturers use the same recipe: 1 level scoop of powder for every 2 fluid ounces of water.

Add powder to pre-measured water, and shake it vigorously. You can mix up one bottle at a time, or mix a full day's worth and refrigerate it.

Liquid concentrate. This dense liquid also gets mixed with water.

To fill a 2-ounce bottle, add 1 ounce of water to 1 ounce of liquid concentrate, then shake vigorously.

Mix one bottle at a time; or prepare a day or two's worth, refrigerate, and use within 48 hours.

Ready-to-Feed. Simply open and pour the ready-made formula into your baby's bottle. No measuring or mixing is necessary.

Ready-to-feed formula comes in 2-, 6-, or 8-fluid-ounce containers. Once it's opened, cover any unused formula and refrigerate it for up to 48 hours.

Whichever type you choose, be sure to follow the directions exactly.

"It is important to mix formula exactly as it is written on the container," Hes says. It's been designed to give your baby the exact nutrition he needs, and it's based on many hours of research.

The right temperature is anywhere from cool to lukewarm. If your water is safe, it's OK to mix powder with room temperature water right from your tap. Never put a bottle in the microwave, which can create hot spots that cause burns.

If you want to warm formula, here are some ways to do it safely:

  • Run the bottle under very warm or hot water. A few minutes should do the trick.
  • Fill a pan with hot water. Remove it from the heat. Place the bottle in the pan for a few minutes.
  • Use a bottle warmer from a baby supply store.

After warming the bottle, shake it vigorously. Test it by squirting a drop on the inside of your wrist. If it's hotter than lukewarm, let it cool before giving it to baby.

Most newborns drink about 1.5 to 3 ounces of formula every 2 to 3 hours. But this varies widely. It's normal for infants to eat different amounts at different feedings.

For premature or low-birth-weight babies, both the amount and timing of feedings vary. "It's best to consult your pediatrician with any questions," Saltzman says.

DON'T water formula down. You might be tempted to eke out more servings, but diluting formula is dangerous. It takes away important nutrients your baby needs and can lead to slower growth and development. It can also lead to water intoxication, which can cause seizures.

DO be clean. Wash your hands before preparing the formula. Make sure your measuring cup is spotless, too.

DON'T use water that's not safe. If you use well water or your town's supply has problems, boil the water first. Or you could choose bottled water. If you boil it, give it time to cool off before mixing it with formula.

DON'T let formula sit around. When it's mixed and ready to drink, give it to baby or store it in the refrigerator within 1 hour. Toss prepared formula that's been sitting at room temperature for more than an hour. Throw away formula your baby didn't finish.