Infant formula: 7 steps to prepare it safely

How you prepare infant formula can make a difference in your baby's health. With their immature immune systems, babies are more susceptible to infection than are older children. Infants are also growing rapidly, and proper mixing of formula ensures they get adequate nutrition to support appropriate growth. Follow these seven steps to prepare infant formula safely and avoid food-related illness.

1. Check the expiration date and condition of the can

Look for an expiration or "use by" date on the can of formula. 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 Don't buy or use outdated infant formula.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 can. Don't use formula from cans with bulges, dents, leaks or rust spots. Formula in a damaged container may 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 your fingernails and the spaces between your fingers.

3. Prepare your utensils

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

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

After first use, you can wash these items with soap and water and air-dry them. Consider rinsing nipples daily in a ratio of 1-to-1 vinegar to water solution and air-drying them, which can help prevent fungal growth.

Also make sure that nipples are open. See if you can squeeze clean water through them. When the nipples are open, put a clean nipple on each bottle and cover it with a nipple cap.

When opening a new can of formula, wash the top with soap and water. Rinse well to remove dirt. Wash the can opener with soap and hot water.

4. Measure the formula

For ready-to-use formula:

• Shake the can of formula well before opening it.
• Pour enough formula for one feeding into a clean bottle.
• Use only formula — no added water or any other liquid.

For liquid concentrate formula:

• Pour the amount of formula for one serving into a clean bottle.
• Use the ounce markings on the bottle to measure the formula correctly. You may consider using water and a liquid measuring cup initially to ensure the measurements on the bottle are correct.

For powdered formula:

• Use only the scoop that comes in the can.
• Make sure that the scoop is dry.
• Determine the amount of formula you wish to prepare, following instructions on the package.
• Fill the scoop with enough formula for the desired serving amount of prepared formula.
• Shave off any excess formula with the flat side of a knife, not a spoon or any other curved surface. Don't pack powder unless specified according to the package instructions.

5. Add water to liquid concentrate or powdered formula

When using liquid concentrate or powdered formula, you'll also need to add water to the bottle. Consider using sterile water:

• If you're using tap water, use cold water.
• If you haven't used a faucet for more than six hours, let the cold water run for as long as it takes to get as cold as it gets — up to two minutes — to help reduce the amount of lead and other contaminants.
• Pour the cold water into a clean pan and boil it for one to two minutes. Boiling water from a local water utility may not be necessary, but it can be helpful if you use private well water, for example.
• Let the water cool.

If you're using bottled water, also consider boiling it for one to two minutes and then let it cool.

See the instructions on the can for how much water to mix with the formula. Adding too much water may overly dilute the formula — meaning that your baby doesn't get enough calories and nutrients. Adding too little water can put a burden on your baby's digestive system.

Before you feed your baby, shake the bottle well.

Don't overdo fluoridated tap water
Exposure to fluoride during infancy helps prevent tooth decay during childhood and beyond. But it's possible to have too much of a good thing. Regularly mixing a baby's formula with fluoridated tap water can provide enough fluoride to cause fluorosis. Signs of fluorosis range from:

• Mild white streaks on the teeth
• More severe pitting or staining of tooth enamel

These stains occur on both baby teeth and permanent teeth.

Levels of fluoride in tap water vary depending on where you live. If you use liquid concentrate or powdered formula:

• Check with your local water utility for specific information about levels of fluoride in your tap water.
• Talk to your child's doctor about what kind of water to use.

Occasional use of water with optimal levels of fluoride will not increase your child's risk of fluorosis. However, your doctor may recommend other water sources lower in fluoride, such as distilled bottled water. In addition, if you have high levels of fluoride in your tap water, know that boiling water will only concentrate it. So, if you're boiling your water, you may want to consider another water source.

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 may 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

If you prepare and fill several bottles at once:

• Label each bottle with the date that the formula was prepared.
• Refrigerate the extra bottles until you need 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. Follow the manufacturer's instructions, and, when in doubt, discard after 24 hours.
• Do not freeze bottles.

If any formula is left in the can, cover and refrigerate it. Use the leftover formula within 24 to 48 hours.

Store unopened cans in a cool, dry indoor place. Don't store these cans in a car or garage, where extreme temperatures can affect the quality of the formula.