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Formula Feeding: Safety and Storage Tips

Updated: Mar 1

As a new parent, taking care of your baby's nutritional needs can be an overwhelming responsibility. If you are reading this article, you are probably considering whether to give your baby formula, either exclusively or as a supplement to breastfeeding.

This might feel like one of the weightiest decisions you've made so far for your child's health, but try not to worry!

Although formula feeding might seem daunting at first, Pathfinder Health is here to help!

In this article, we'll explain all the basics of baby formula so you feel more confident navigating this foundational step in the nutritional journey for your little one.

In this article:

What is baby formula?

Baby formula is an alternative to breast milk designed for families where (1) parents cannot--or choose not to--breastfeed or (2) babies either cannot nurse or are unable to drink breast milk for medical reasons. It is formulated to meet all of a growing baby's nutritional needs so that it can be used as a full substitute for breast milk.

For purposes of this article, we will be discussing infant formula intended for babies under one year old. After your baby turns one, they are ready to drink whole cow's milk, unless they have an allergy or other health concern.

Regular formula

Most infant formula is made with cow’s milk that has been specially formulated so it has the same balance of nutrients as breast milk but can be easily digested by a baby's delicate tummy.

Nutritionally speaking, it doesn’t matter if you buy name-brand or generic formula. However, you should choose infant formula that is fortified with iron, an essential nutrient for your baby’s growth and development.

Infant formulas come in three types

Different brands of baby formula have slightly different tastes. You might need to try more than one brand before finding one that your baby likes, especially if they have previously been breastfed, so be patient if you are making this transition.

Special formula

Most babies can easily digest cow's milk formula with no adverse reactions. However, 1-2% of infants are allergic to the proteins in cow’s milk and require special formula. Of these babies, up to 50% are also sensitive to soy protein and require an even more specialized formula.

If you suspect that your baby has an allergy or sensitivity, consult with your pediatrician and follow their feeding recommendations precisely. Do not start your baby on a special formula without medical guidance.

Is baby formula nutritious for babies?

The short answer: Yes, it is! Although different formula manufacturers may vary their formulations, all infant formula sold in the US is required to meet nutrient standards set by the Food and Drug Administration (FDA).

So don't feel guilty if you need--or choose--to feed your baby formula. They will still receive the nutrients they need to grow and you can still bond by holding them close while you feed them.

Feeding your baby with formula

Choosing bottles

There are no special bottles required for formula feeding. Just make sure that you are using bottle nipples with a flow rate that is appropriate for your baby’s age, health, and feeding style.

Preparing infant formula

If all of this guidance sounds daunting, don't despair! Infant formula preparation may sound complicated at first, but it will soon become second nature to follow all of these precautions and recommendations when preparing bottles.

Just make sure you follow the manufacturer’s instructions.

Safety precautions

Safely prepared infant formula is essential to your baby's health. The following precautions will help to minimize the risk of bacteria or other contamination and protect your baby:

  1. Be sure to check the expiration date on the package--you should never use formula past this date. Also make sure that the formula container does not have any cracks or dents.

  2. Always wash your hands thoroughly or use hand sanitizer before preparing a bottle of formula and/or feeding your baby.

  3. Be sure to use a fresh bottle for each feeding.

  4. Mix formula on a clean, sanitized surface. Do not place formula lids or scoops on contaminated surfaces, such as countertops or sinks.

Mixing infant formula

In general, tap water is safe to use in mixing formula, unless there are known contaminants in your area. Always use cold tap water and warm the formula after it is mixed.

If you are concerned about the safety of your tap water, you can boil it first. Simply bring water to a rolling boil, boil for ten minutes, and then let it cool to room temperature or slightly above before using.

Note that boiling only kills bacteria--it does not get rid of lead or other non-biological contaminants. Another alternative is to use bottled water.

You should also use bottled or boiled water to prepare formula if your baby is less than two months old, was born prematurely, or has a weakened immune system. Talk to your healthcare provider about any other steps that you should take for a higher risk baby.

Otherwise, when preparing formula, it is essential to follow the formula package directions regarding safe handling and mixing, in particular the correct ratio of water to formula.

We understand that formula is expensive and it can be tempting to use a higher ratio of water to “stretch” the formula and make it last longer. However, this can be extremely dangerous for your baby.

Watering down your baby's formula reduces the amount of nutrients they receive in a bottle, which can impact their growth and development. Adding extra water also throws off the balance of electrolytes and minerals in the formula, which can lead to kidney damage and seizures.

Warming bottles

Although it is perfectly fine for babies to drink cold formula, some parents may choose to warm up the formula before feeding it to their baby. In fact, it will likely be more palatable for babies that are also breastfed and are accustomed to drinking warm breast milk.

Warming formula is fine, as long as the person feeding the baby tests the warmed formula to make sure that it's not too hot.

If you do warm your baby’s bottles, you can use a bottle warmer or simply put the bottle in a bowl or mug of hot water for a few minutes. Swirl the bottle gently to even out the temperature.

Before feeding your baby, shake a few drops on the inside of your wrist to test the temperature.

You should never microwave a baby’s bottle–this can create “hot spots” that could burn your baby's mouth.

After your baby's feeding

Discard any unused formula left in the bottle one hour after the feeding begins.

Be sure to clean your baby's bottles thoroughly. You can wash bottles by hand in hot soapy water or put them in the dishwasher.

Storing formula

Storing formula safely is critical to your baby's health.

Keep containers of formula powder inside your home in a cool, dry place. Do not store it in the refrigerator or freezer.

You should store unopened containers of concentrated or ready to feed formula in the same way. Opened containers of these types should be kept in the refrigerator.

Most powdered baby formula should be used within one month after the container has been opened. You can write the date of opening on the container itself as a reminder.

Baby formula feeding FAQs

1. What is the best formula for colic?

It depends on the cause of the colic. If your baby has a food intolerance (such as dairy or soy), consult with your doctor about the best type of formula. Otherwise, good feeding practices, such as small meals and frequent burping, are more important than formula brand.

2. Can I prepare formula ahead of time?

Yes. You can premix water and powdered formula for the day, either in individual bottles or in a formula mixer or other large sterile container, and keep the prepared formula in the refrigerator for 24 hours.

3. Can babies drink cold formula?

Yes. There is no medical reason to warm a baby’s bottle—it is perfectly safe for a baby to drink room temperature or even cold formula if they are willing to do so.

4. How long is formula good for after mixing?

Prepared but untouched formula can sit at room temperature for up to 2 hours. If your baby has started feeding, use the formula within 1 hour. After 2 hours (or 1 hour if feeding started), discard any formula left in the bottle.

5. How long is formula good in the fridge?

As long as you promptly put it in the refrigerator and your baby has not started drinking from the bottle, a bottle of unused prepared powdered formula will keep for 24 hours in the fridge. The same time frame applies to unused prepared concentrated formula (also called liquid concentrate formula).

You can store opened containers of ready to feed formula and concentrated formula in the fridge for 48 hours.

When you are ready to feed your baby, remove a bottle of formula from the fridge or pour formula from the larger container and warm it if you wish. Once the bottle has been warmed once, it should not be put back in the fridge and later rewarmed.

6. Can you reheat formula?

No. It is not safe to reheat formula. Once your baby starts drinking from a bottle, you should finish the feeding within 1 hour and discard any formula left in the bottle. Leftover formula can grow bacteria that might make your baby sick—reheating does not kill this bacteria.

7. What if my baby doesn't finish their bottle? Is it okay to save leftover formula?

Once your baby drinks from a bottle, you should discard any unused formula left in the bottle 1 hour after feeding begins. The combination of your baby's saliva and the leftover formula can lead to the growth of harmful bacteria that can make your baby sick.

Pathfinder gets it—it's frustrating and expensive to waste formula. Just remember that this is an important safeguard for your baby’s health. Once you have been feeding your baby formula for some time, you should have a good idea of how much they eat at one feeding and will rarely need to discard very much.

Below is an example to illustrate how long you can safely use prepared formula.

Dealing with formula shortages

Resources for parents

If your baby does not have any special medical or nutritional needs, it is fine to switch to a different brand of formula of the same type.

If your baby requires a specialty formula, check the list of comparable formulas compiled by the North American Society For Pediatric Gastroenterology, Hepatology & Nutrition to see if there is a safe, appropriate substitute. Be sure to consult with your healthcare provider before switching to a different specialty formula.

If you are unable to find suitable infant formula in stores or online, call your child's pediatrician. Pediatricians often have formula samples in stock or can connect you with local organizations that can help you find formula.

Your pediatrician can also help you submit a request for specialty formula through emergency programs offered by formula manufacturers.

Your pediatrician may also advise you about short-term options that you can use in an emergency, such as cow's milk, soy milk, or toddler drinks. You should always consult with your healthcare provider before using any of these short-term options.

You can also try contacting your local Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) clinic to see if you are eligible to receive benefits, including formula.

A note of caution: Do NOT use homemade formula

You may have seen recipes online for making baby formula at home from various ingredients, such as evaporated milk and sugar. Be aware that homemade formula can have serious health implications for your baby--both the FDA and the American Academy of Pediatrics (AAP) caution against using it.

Most of these formulations do not contain the appropriate nutrients in the appropriate amounts that your baby needs to grow and develop, which can lead to severe nutritional deficiencies and other risks.

They can also contain unsafe ingredients for babies, such as honey or raw milk. Additionally, making formula in an unsterile home kitchen can increase the risk of contamination and make your baby sick.

Even though caregivers may have relied on these recipes in the past, today’s medical expertise has shown that they are not the safest option.

The Takeaway

Formula feeding is a lifesaver for many parents for a variety of reasons. Properly prepared and fed to your baby, it provides all of the nutrition that they need and will contribute to their healthy growth and development.


  1. Centers for Disease Control, How To Prepare and Store Powdered Infant Formula, available at

  2. Centers for Disease Control, Cronobacter Infection and Infants, available at

  3. U.S. Department of Health and Human Services (HHS), Information for Families During the Formula Shortage, available at

  4. U.S. Food and Drug Administration, What to Know About the Risk of Cronobacter in Powdered Infant Formula, available at,Abbott%20Nutrition%20in%20Sturgis%2C%20Michigan.

  5. Pados BF, Park J, Thoyre SM, et al. Milk flow rates from bottle nipples used after hospital discharge. MCN Am J Matern Child Nurs. 2016 Jul-Aug; 41(4): 237–243.


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