Mayo Clinic Health Library

Infant formula: 7 steps to prepare it safely

Updated: 01-19-2013

You've chosen your baby's infant formula with care — but are you preparing it properly? Follow these steps to ensure proper nutrition and avoid food-related illness.

1. Check the expiration date and condition of the container

Look for an expiration or "use by" date on the formula container. If the expiration date has passed, you can't be sure of the formula's quality. Don't buy or use outdated infant formula.

While checking the expiration date, also inspect the condition of the formula container. Don't buy or use formula from containers with bulges, dents, leaks or rust spots. Formula in a damaged container might be unsafe.

2. Wash your hands

Before preparing formula, wash your hands thoroughly. Wet your hands with warm running water, then rub soap on your hands vigorously for at least 20 seconds. Wash all hand surfaces, including under your fingernails and in the spaces between your fingers.

3. Prepare your bottle

Sterilize bottles, nipples, caps and rings before using them for the first time:

  • Boil the bottle and accessories in water for five minutes. Use a pot that's large enough to hold all of the pieces and cover them completely with water.
  • Remove the pieces from the water using a clean set of tongs.
  • Allow the pieces to air-dry.

After the first use, there's no need to sterilize your bottle and accessories. Simply wash these items with soap and water and allow them to air-dry. Bottle and nipple brushes can help you clean nooks and crannies. You can also use the dishwasher. If you do so, consider getting a dishwasher-safe basket to hold your utensils.

Also, during the cleaning process, make sure the nipples are open. Hold each nipple upside down and fill it with clean water, then look for the water to drip slowly out of the nipple.

Remember to clean formula containers, too. Before opening a new container, wash the top with soap and water, then rinse well.

If you plan to prepare formula in the bottle, confirm the measuring marks on each bottle. Simply use a liquid measuring cup and water to make sure the measurements on the bottle are accurate.

4. Add water to liquid-concentrate or powdered formula

If you're using liquid-concentrate or powdered formula, you'll need to add water to the bottle. Check to see if the manufacturer's instructions specify whether to add water or formula to the bottle first. Typically, you'll add water to the clean bottle first to ensure you're using the proper amount.

Follow the manufacturer's instructions for how much water to use. Adding too little water can put a burden on your baby's digestive system, and adding too much water might overly dilute the formula and deprive your baby of calories and nutrients.

You can use any type of clean water — tap or bottled — to prepare liquid-concentrate or powdered formula. If you'd like to use tap water but you're concerned about the safety of your water supply or you use private well water, consider sterilizing the water before adding it to the bottle:

  • Use cold tap water.
  • Let the cold water run for as long as it takes to get as cold as it gets — up to two minutes. This helps reduce the amount of lead and other contaminants in the water.
  • Pour the cold water into a clean pan and boil it for one to two minutes.
  • Let the water cool.
  • Carefully pour the amount needed.

You might also have well water checked for lead, nitrates and bacteria.

It's also important to consider the amount of fluoride in the water you use to prepare your baby's liquid-concentrate or powdered formula. Exposure to fluoride during infancy helps prevent tooth decay during infancy. However, regularly mixing a baby's formula with fluoridated water might increase your child's risk of developing faint white markings or streaks on the teeth — a sign of mild enamel fluorosis.

If you're concerned about fluorosis, consider ways to minimize your baby's exposure to fluoride. For example, you might use ready-to-feed formula or alternate between tap water and low-fluoride bottled water — such as purified, demineralized, deionized or distilled bottled water — for formula preparation. However, if you feed your baby only ready-to-feed formula or concentrated formula mixed with low-fluoride water, your baby's doctor might recommend fluoride supplements beginning at 6 months.

5. Measure the formula

For ready-to-use formula:

  • Shake the container of formula well before opening it.
  • Pour enough formula for one feeding into a clean bottle.
  • Use only formula — don't add water or any other liquid.
  • Attach the nipple and cap and shake well.

For liquid-concentrate formula:

  • Shake the container of formula well before opening it.
  • Pour the amount of formula for one serving into the bottle, which already contains the appropriate amount of water.
  • Attach the nipple and cap and shake well.

For powdered formula:

  • Use the scoop that came with the formula container. Make sure the scoop is dry.
  • Determine the amount of formula you want to prepare, following instructions on the package. Note the number of scoops you'll need.
  • Fill the scoop with powdered formula, shaving off any excess formula from the top of the scoop with the flat side of a knife — not a spoon or other curved surface.
  • Pour the scoop or scoops into the bottle, which already contains the appropriate amount of water.
  • Attach the nipple and cap and shake well.

6. Warm the formula, if needed

It's fine to give your baby room temperature or even cold formula. If your baby prefers warm formula:

  • Place a filled bottle in a bowl or pan of hot, but not boiling, water and let it stand for a few minutes — or warm the bottle under running water.
  • Shake the bottle after warming it.
  • Turn the bottle upside down and allow a drop or two of formula to fall on your wrist or the back of your hand.
  • The formula should feel lukewarm — not hot.

Don't warm bottles in the microwave. The formula might heat unevenly, creating hot spots that could burn your baby's mouth.

Shake the bottle well and feed the formula to your baby immediately. Discard any formula that remains in the bottle after a feeding.

7. Store formula safely

Store unopened formula containers in a cool, dry place. Don't store formula containers outdoors or in a car or garage, where temperature extremes can affect the quality of the formula.

If you're using ready-to-use formula, cover and refrigerate any leftover formula from a freshly opened container. Discard any leftover formula that's been in the refrigerator more than 48 hours.

If you prepare and fill several bottles of liquid-concentrate or powdered formula at once:

  • Label each bottle with the date that the formula was prepared.
  • Refrigerate the extra bottles until you need them — don't freeze them.
  • Put the bottles toward the back of the refrigerator, where it's coldest.
  • Discard any prepared formula that's been in the refrigerator more than 24 to 48 hours.

If you're unsure whether a particular container or bottle of formula is safe, throw it out.