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

Why It Matters

"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 Measure and Mix

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

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.