How to prepare formula: A step

It's normal to have questions about how to prepare formula. Here's the standard how-to.

When you’re a parent ready to shift from breast to bottle or a caregiver new to infant feeding, it's normal to have questions about how to prepare formula. Which goes first, the water or the formula? Should the water be cool or warm? And what do you do if there's formula left over?

"Providing an infant with the proper nutrition is critical to their development and growing along a healthy curve," says Emily Silver, a Charlestown, Massachusetts, family nurse practitioner, lactation consultant and co-founder of parent support platform NAPS. "In general, it's good practice to get familiar with your own formula and carefully read its guidelines for preparation and safe storage, as different brands can vary."

But don't worry. Though you should always refer to the instructions on the formula label, there is a standard procedure for safely preparing a bottle of baby formula. Here's how.

There are a few things the Centers for Disease Control and Prevention (CDC) says to check before preparing a bottle:

"Expired formula should not be used since critical ingredients may be past their prime, leaving the baby at risk of a nutritional deficiency," says Dr. Natasha Burgert, a Kansas-based pediatrician, and spokesperson for Philips Avent and the American Academy of Pediatrics (AAP).

Make sure any new container of formula is sealed. A rusted or unsealed container could mean the contents are contaminated, making the formula unhealthy for the baby.

Babies and toddlers have different nutritional needs. The CDC recommends double-checking that your formula label matches the infant's age.

It's also important to be aware of recent safety recalls to ensure you’re feeding the baby a safe formula, says Silver.

It's vital to wash your hands before preparing a baby's bottle, says Silver.

The CDC offers these guidelines for handwashing before food preparation:

Never mix formula in a bottle that hasn't been recently washed. "Bottles themselves can be contaminated with bacteria, so proper cleaning and storage is best practice," says Burgert.

If you’ve taken the bottle out of the package for the first time, you should sanitize it. The CDC also recommends daily bottle sanitizing for babies born prematurely, younger than 2 months, and with compromised immune systems.

Here are three bottle sanitizing methods suggested by Burgert:

"Daily maintenance should include washing parts with hot soapy water, steaming or dishwashing," says Silver.

To handwash a bottle before preparing formula, follow these steps:

Always add the water to the bottle before adding liquid-concentrate or powdered formula. This is critical to measuring and mixing the formula correctly.

"Ingredients need to be rehydrated correctly so a dangerous imbalance is not created," says Burgert. Too little water causes digestion issues, she explains, while too much water can dilute calories and impede infant growth.

Here's how to prepare the water:

It's perfectly safe for babies to drink room temperature or even cold formula, says Burgert. She adds, "Getting your baby used to drinking room temperature formula can make bottles on-the-go much easier."

If you want to warm the bottle anyway, do not use the microwave. Silver says this can produce dangerous "hot spots" that will burn the baby's mouth.

Here's how she recommends warming a bottle:

Once the formula is mixed, give it to the baby or refrigerate it immediately. You should discard any prepared formula that isn't used within 24 hours.

Some caregivers find it helpful to prepare a few bottles or a lidded container of formula all at once. To do that, label the container with the date and time and be prepared to discard any leftovers after 24 hours.

Silver says you can mix most formulas in advance if you refrigerate and use them within 24 hours.

"If parents are using a lot of formula, they can make a batch, similar to a pitcher of lemonade, and keep it prepared in the fridge for easy access," she says.

Not necessarily, says Silver. "Commonly, packaging on formula reads to use filtered or boiled water. This is because it's a global recommendation," she explains. But if your tap water is clean, it might not need to be boiled. Contact your health department to find out if your local tap water is safe for infant formula.

It's not necessary to warm infant formula, though that doesn't mean your baby won't have a preference.

Bergert notes, "It's perfectly fine for your baby to drink room temp or even cool formula."