Safe preparation and storage of infant formula are important for your baby's health. Follow these steps to make sure your baby's formula is nutritious and safe.

Look for an expiration or "use by" date on the formula container. You can't be sure of the formula's quality after that date. Don't buy or use expired infant formula.

Before preparing formula, wash your hands thoroughly with soap and water. Dry your hands well. Clean the area where you will prepare the formula.

Sterilize bottles, nipples, caps and rings before using them for the first time. You can sterilize them with any of these methods:

• Boil the bottle and accessories in water for five minutes.
• Use a microwave steam sterilizer bag.
• Use a stand-alone electric steam sterilizer.

After the first use, you usually don't need to sterilize bottles and their parts. Wash these items with soap and hot water. Bottle and nipple brushes can help you clean them well. You also can use a dishwasher.

You might continue sanitizing the bottle if your baby:

• Is younger than 3 months.
• Was born prematurely.
• Has a weakened immune system.

Formula comes in three forms:

• Ready-to-feed liquid.
• Concentrated liquid.
• Powder.

Do not add water to ready-to-feed liquid formula. You will need to add water to concentrated liquid and powder formulas. Follow the instructions on the product label.

Water safety

You can use clean tap water or bottled water for concentrated liquid or powder formula. Other safety tips are:

• Ask your public water supplier to test for lead in your water. If you have concerns, talk to your health care provider about lead testing for your child.
• If you use well water, have the water tested for chemicals, germs or minerals that may be harmful. Your local health department may provide a testing service.
• If you use well water or are concerned about water safety, boil the water for one minute. Measure the water after boiling and let it cool to room temperature.

Fluoride

Most public water supplies have fluoride added. Fluoride is important to prevent tooth decay. But too much fluoride can increase the risk of faint white lines or streaks on the teeth, called fluorosis.

If your baby drinks only concentrated or powder formula, you might switch between fluoridated tap water and low-fluoride bottled water. Labels on these bottles will say:

• Deionized.
• Purified.
• Demineralized.
• Distilled.

If your baby uses only ready-to-feed formula or you only use low-fluoride bottled water for formula, talk to your health care provider. After age 6 months, your baby may need fluoride supplements. This might be done by using fluoridated bottled water called nursery water. Or you may need to give your baby fluoride drops.

Carefully measure the amount of water and formula. Too much water might mean your baby doesn't get enough nutrients. Too little water might cause your baby to have digestive problems or not have enough fluids.

For ready-to-use formula:

• 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 to the bottle.

For liquid-concentrate formula:

• Pour the amount of water needed into a clean bottle.
• Pour the amount of formula needed into the bottle.
• Attach the nipple and cap to the bottle and shake well.

For powdered formula:

• Determine the amount of formula you want to prepare, following instructions on the package.
• Measure the amount of water needed and add it to a clean bottle.
• Use the scoop that came with the formula container to scoop the powdered formula. Add the number of scoops needed into the bottle.
• Attach the nipple and cap to the bottle and shake well.

If your baby is younger than 3 months, was born prematurely or has a weakened immune system, take these additional steps. These steps can reduce the risk of illness from cronobacter bacteria:

• Boil the water for one minute.
• Measure the water after boiling.
• Let cool for five minutes.
• Prepare the formula.
• Put the bottle under cold running water or in an ice bath to cool. The formula should be at body temperature, 98.6 degrees Fahrenheit (37 degrees Celsius).
• Test that the formula is lukewarm — not hot — by putting drops on your wrist or the back of your hand.

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 of warm water or run under warm water.

Test the temperature by putting a couple of drops on the back of your hand or wrist. 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.

Use the formula within one hour after the beginning of feeding. Throw away formula left in the bottle and do not store it in the refrigerator. Bacteria from your baby's saliva can grow in the formula.

If you're using ready-to-use formula, cover and refrigerate any unused formula from a freshly opened container. Discard any leftover ready-to-use 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, do the following:

• Label each bottle with the date and time that the formula was prepared.
• Refrigerate the extra bottles until you need them.
• Discard any prepared formula that's been in the refrigerator more than 24 hours.

If you're not sure whether a container or bottle of formula is safe, throw it out.