How to Prepare Baby Formula

Baby drinking from bottle

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Preparing baby formula is a pretty simple process. Essentially, you are mixing the formula powder with water. However, you may wonder whether you need to use boiled water and if there are other recommended steps to follow. 

When preparing baby formula, it is important to mix it correctly with safe drinking water. Additionally, it's important to follow the directions on the formula's packaging. As you are learning how to prepare baby formula, it helps to know the guidelines and recommended preparation methods, generally and for your specific formula brand, to ensure your baby's safety.

Be sure to share instructions on formula preparation methods with whoever will be taking care of your baby, whether it is child care providers, grandparents, babysitters, or other family members. And know that recommendations can vary depending on your location and access to safe drinking water, as well as the type of formula you use. Learn more about how to safely prepare baby formula.


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How to Prepare and Store Infant Formula

The World Health Organization (WHO) has issued guidelines for the safe preparation, storage, and handling of powdered infant formula.

Boiling water when preparing baby formula is very important in many parts of the world, especially developing countries that do not have safe water supplies.

The WHO recommends cleaning and sterilizing feeding and preparation equipment and making a fresh bottle of powdered infant formula for each feed. The recommended steps for preparing formula are:

  1. Clean and disinfect all of the surfaces that you will be using, and wash your hands properly.
  2. Boil water, even if it is bottled water.
  3. Let the water cool (for no more than 30 minutes) and pour it into a cleaned and sterilized bottle.
  4. Add the exact recommended amount of powdered formula to the water.
  5. Assemble the bottle and mix the powdered formula thoroughly.
  6. Quickly cool the bottle by holding it under running tap water or by placing it in a container of cold water or iced water.
  7. Dry the outside of the bottle with a clean cloth.
  8. Check the temperature of the formula so that it doesn't burn your baby's mouth.

Follow baby formula mixing instructions carefully and don't dilute or concentrate the baby formula unless your pediatrician tells you to.

Steps for formula

Verywell / Jessica Olah  

Baby Formula Safety

After you prepare your baby's formula, you should follow some simple rules to keep your baby safe. Unless you refrigerate the prepared formula, feed it to your baby within two hours. If you do put the prepared formula in the refrigerator, be sure to use it within 24 hours. Don't warm baby bottles in the microwave. Instead, use a baby bottle warmer or place the bottles in a container of warm water.

Once your baby starts drinking from a bottle, discard any formula that isn't finished within two hours, and don't put the bottle back in the refrigerator. The unused formula should not be saved for later. If you find yourself throwing away large amounts of formula, consider preparing a smaller amount next time so that you don't have so much left over.

Safe Drinking Water

It is vitally important that you use safe drinking water in your baby's formula. However, the term "safe drinking water" is vague and general, and you may question whether your tap water is safe and whether it should be boiled before using. The answer depends largely on whether there is a chance that the water you are using could be contaminated with infectious microorganisms.

Using Cold Tap Water to Avoid Lead Contamination

When using tap water for baby formula, always use cold tap water that has run for 15 to 20 seconds rather than warm or hot tap water. The reason for this is that many homes have plumbing with lead or lead solder, and hot water can concentrate the lead, which is a risk factor for lead poisoning.

Unless you have an inline hot water heater, your hot water has sat in a hot water tank and may be contaminated with lead. Running the water to ensure a fresh flow and only using cold water can help reduce your baby's exposure to lead from tap water.

According to the U.S. Environmental Protection Agency, you should never mix baby formula using hot water from the tap.

Boiling water doesn't get rid of lead. Many home water filters, including pitcher and faucet filters, do remove lead from drinking water.

Boiling Water to Avoid Infection

The advice to boil water is based on the idea that hot temperatures can kill most microorganisms. For those using tap water from public water supplies, there is little danger, as the water supply is constantly monitored and warnings are issued if there is a risk of contamination. But because babies have weaker immune systems, many parents choose to boil tap water.

In addition, using freshly boiled water can kill any bacteria that may be in the formula itself. This is beneficial, unless the formula contains added probiotics. Boiling water will kill the probiotics.

In the past, packaging on infant formula stated that water should be boiled prior to preparation. The American Academy of Pediatrics (AAP) recommends that if you have any concerns about whether your tap water is safe, you should boil it for up one minute and then use the boiled water within 30 minutes to mix the formula.

However, the AAP does not make an official statement about whether you need to boil the water that you will use in mixing your baby's formula. Instead, it recommends that you check the safety of your water with the local health department.

In some instances, your baby may be safer if you boil the water before mixing formula. This is especially true if you are traveling out of the country, where your baby can be exposed to unfamiliar infections through the water. If you are using well water, boiling will not remove impurities and chemicals, and you should have your water tested for contaminants before using it.

Are There Downsides to Boiling Safe Water?

If your tap water is safe to drink, should you still boil it before using it to mix formula? This is a complicated question. There are two major downsides:

  • It complicates feeding at a time when most caregivers are stretched very thin already.
  • It raises the risk of burns to the caregiver and the infant.

The AAP recommends boiling water if you are uncertain about the safety of your water source.

Sterile Water

Purified, filtered, or bottled water should have fewer impurities and contaminants than tap water, including lead. It could still have bacteria, which may be killed by boiling.

Generally, breastfeeding is recommended for infants in high-risk situations, especially for premature babies in the neonatal intensive care unit. If you are using formula to feed your premature or sick baby, a sterile liquid baby formula or powdered formula mixed with sterile water is recommended.

Fluoride and Preparing Baby Formula

Experts often recommend that children should get fluoridated water to help prevent cavities. However, powdered formula is often fortified with fluoride too, so infants who are fed powdered or concentrated liquid formula which is mixed with fluoridated water can get too much fluoride.

Getting too much fluoride when your child's teeth are still forming can lead to enamel fluorosis, which can cause tooth staining. This staining may appear as faint white markings on your child's baby teeth, and even more importantly, may also affect permanent teeth as they are forming underneath your baby's gums.

Fortunately, fluorosis is usually very mild when it is caused by fluoridated water and baby formula and the staining is barely noticeable. You don't have to be concerned about fluorosis if you're breastfeeding your baby or using a ready-to-feed baby formula, and supplement with powdered formula.

To reduce your baby's chance of developing even mild fluorosis, it can help to use low-fluoride water (less than 0.7 mg/L) when you prepare your baby's formula. This may mean some types of tap water, or water that has been purified, deionized, demineralized, distilled, or filtered by reverse osmosis.

A Word From Verywell

As more and more adults have switched to bottled water rather than tap water, it is natural to have concerns about using tap water for infant formula. Talk to your pediatrician to see if you need to boil your water, especially if you are using well water that hasn't been recently tested, or if you aren't convinced that the tap water where you live is safe and healthy for a baby.

7 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Wilkinson TA, Scott EK, Carroll AE. Mixed message on formula mixing. Pediatrics. 2019;143(6):e20182525. doi:10.1542/peds.2018-2525

  2. World Health Organization. Safe preparation, storage and handling of powdered infant formula. Updated 2007.

  3. U.S. Environmental Protection Agency. Basic information about lead in drinking water. Updated November 18, 2019.

  4. American Academy of Pediatrics. How to safely prepare formula with water. Updated July 3, 2018.

  5. Centers for Disease Control and Prevention. Well testing. Updated April 10, 2009.

  6. Centers for Disease Control and Prevention. Infant formula. Updated November 3, 2015.

  7. Centers for Disease Control and Prevention. Fluorosis. Updated March 8, 2019.

Additional Reading

By Vincent Iannelli, MD
Vincent Iannelli, MD, is a board-certified pediatrician and fellow of the American Academy of Pediatrics. Dr. Iannelli has cared for children for more than 20 years.