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By Agustina Fernandez January 19, 2023 8 min read
Reviewed by Dr. Po-Chang Hsu, MD, MS
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If you're a newcomer to the wonderful world of parenthood, we're willing to bet that you've been spending a lot of time researching and learning everything you can about babies.
One of the most important things many new parents have to inform themselves about is safe practices for formula feeding their little ones.
Preparing your infant's formula correctly can help safeguard your baby against bacterial illness and food poisoning.
To help you learn the ropes more quickly, we've prepared a helpful guide that covers the usual formula feeding FAQs on how to prepare, store, and serve formula!
Many mums and dad across the globe formula feed their infants. If this is the case for your family, safely prepared infant formula is paramount to your little one's health.
Just to get some basic principles out of the way, please note you must check the expiration date of infant formula before buying it and before feeding it to your child. It’s never safe to use baby formula after the expiration date.
Moreover, you should never feed your baby formula if the packaging is damaged. Scroll down to learn more about proper baby formula preparation and storage!
So, let's say that your little one has drank some of their bottle but they don't want the rest, what should you do? Well, in this case, you’ll need to use it within the hour or throw it out.
After an hour, if you're wondering if it can still be used the short answer to this question is a hard no¹, it is absolutely not safe to use unfinished formula leftover from feeding and it should not be saved in the refrigerator.
The reason for this is that the mixing of saliva from your baby's mouth with infant formula can cause harmful bacteria to grow in your baby's bottle³.
Plus, milk-based food products like infant formulas, are particularly infamous for speedy bacterial growth.
The best practices for preparing infant formula are to always thoroughly clean and sanitize the bottle before using it for feeding and when it comes to unused formula after a feeding, the only place it belongs is down the drain!
Learn more: What Kind of Water is Safe for Babies?
Generally speaking, after you've prepared formula for your little one if you don't use or heat the prepared infant formula it should be refrigerated immediately and used within 24 hours.
More specifically, health organizations such as the Centre for Disease Control (CDC) and the American Association of Pediatrics (AAP) advise that unused prepared powdered formula can safely be stored in the fridge for up to 24 hours².
In terms of unused opened bottles of ready-to-feed formula or prepared liquid concentrate formula, it can safely be stored in the fridge for up to 48 hours.
It's important to always follow the preparation guidelines of the specific formula you are using as some manufacturers will have a shorter duration in which their formula is safe to use after preparation.
Prepared baby formula is best kept in refrigerators that are 40°F (4.4°C) or cooler. But make sure it's not too cool, if you freeze the formula, that can change its texture.
And to put any myths you may have heard to rest, the freezing of formula does help formula last longer. Finally, remember that unmixed formula has no place in your fridge and should not be stored there!
Bacteria thrive at room temperature so once you've mixed your little one's powdered infant formula and water together to create a nourishing meal for your little bundle of joy, the countdown until it spoils begins!
As a general rule, if you let untouched and unheated infant formula sit at room temperature, it should be used within 2 hours. The standard is typically the same for both powdered formula and ready-to-feed formula.
However, many of the EU organic formulas that we offer at our shop are only considered safe to use within one hour after being mixed and sitting at room temperature. So, be sure to check the manufacturer's specific guidelines!
For those of you with babies who like warm formula, the guidelines are a little less forgiving. The untouched formula that has been heated should be fed to your baby within one hour after mixing.
As an additional note of caution here, a warmed unused bottle of formula should not be put back in the refrigerator for later use.
It's not hard to see that as a new parent, you often have your hands full. Like many moms and dads, you're probably searching for time-saving hacks because anywhere you can spare a minute or two will certainly add up.
Well, more power to you! We respect your hustle and totally agree that you deserve a break! But unfortunately, when it comes to infant formula preparation, this is usually not the place to try and save time.
Proper formula preparation is essential to the health of your baby's delicate tummy, so short-cuts are discouraged. The safest method for infant formula preparation is to prepare your baby's bottle fresh, right before feeding begins!
While this is the gold standard for making up formulas, we realize that it may not be obtainable 100% of the time. In such cases, some parents may choose to make up their baby's bottles for the whole day and store them in the refrigerator.
If you must go this route be sure to only make enough prepared formula based on what your baby drinks in 24 hours.
As we've covered you can generally use formula mixed, untouched, and unheated for up to 24 hours in the case of powdered formula and up to 48 hours in the case of ready-to-feed formula.
A good strategy for storing formula safely for later use is to place the bottles closer to the back of the fridge which tends to stay cooler than the door compartments. You may wish to arrange the bottles in such a way that the newest bottles are behind the older bottles up front, that way you’re always using the older bottles first.
The downside to preparing bottles in advance is that while it may very well make your life easier, it also comes with an increased risk of bacterial contamination which could make your baby sick⁴.
If you're looking for a more safe happy medium between preparing formula fresh and in advance, some health care professionals have recommended that parents pre-measure the water and formula powder before feedings to make preparation quicker.
Most infant formulas will stay good up until 1 month after opening, but of course, there are variations between manufacturers so your reference point should always be the guidelines of your baby's specific formula!
On the day that you open the infant formula containers, a good strategy is to write the date on the lid so that you can remember exactly how long you have to use the formula until it spoils.
To make things a little easier for you we've made a chart for all the EU organic formula brands that we offer that explains how long you have to use them after opening the formula container.
Unlike powdered formula, ready-to-feed formula tends to be a little more pricy, this is because it offers parents greater convenience and ease of use when compared with powdered formulas.
P.S, if your baby has a weakened immune system or was born prematurely, the CDC advises feeding your baby with a liquid formula as these tend to be more sterile and can help protect your little one against Cronobacter infection⁵. In any case, you'll need to speak with your pediatrician first to find out what's best for your little one.
An unused opened container of ready-to-feed infant formula should be used immediately or safely stored in the fridge for up to 48 hours⁶.
Again, some manufacturers will have a slightly different use by window so it's best to check the guidelines of your baby's specific formula if you’re looking to find out how long it can last.
We know how important it is for you to have an ample supply of formula on hand to nourish your baby. That's why, when you shop with us, we guarantee that you'll receive the freshest batch of formula from us with an expiration date of 6 months or more into the future. Plus when you buy in bulk, it not only saves you some coin but it also means less shopping for you down the line!
So once you receive your formula milk from us, what is the best way to safely store your infant formula container? There are some pretty straightforward rules surrounding formula storage.
According to the CDC, it is best to store unmixed formula in a cool and dry place, unsafe places to store formula are outdoors or inside vehicles or garages. Additionally, it's important to make sure the formula lid or bag is tightly secured.
Phew, that was a lot of ground that we just covered, no one ever said infant formula didn't have a lot of rules. We know it can be a lot to digest all of that information, but it's important to prepare your little one's formula correctly because young babies have sensitive tummies that require the utmost care when it comes to feeding.
But don't fret, you'll get into the swing of things and soon enough you'll master the art of formula preparation! The most important thing to remember is to always follow the preparation instructions of your baby's formula exactly, store it safely, and never reuse leftover formula or use infant formula past its expiration date.
If you're ever unsure about the best practices for your formula-fed baby, be sure to consult your pediatrician. Happy feeding!
Please be aware that this information is based on general trends evidenced in babies, it is in no way medical advice. Your doctor should be your first source of information and advice when considering any changes to your child’s formula, and when choosing your child’s formula. Always consult your pediatrician prior to making any decisions about your child’s diet or if you notice any changes in your child.
Disclaimer: Breastfeeding is the best nutrition for your baby, because breast milk provides your child with all the essential nutrients they need for growth and development. Please consult your pediatrician if your child requires supplemental feeding.
How long does baby formula last? Forbes. May 24, 2021.
Infant formula preparation and storage. Centre for Disease Control. 2022.
How long is infant formula good for once mixed? And other questions about formula. Healthline. December 19, 2019.
Preparing, using, and storing formula safely. Baby Centre. April 13, 2022.
Cronobacter infection and infants. Centre for Disease Control. 2022.
Formula feeding faqs: Preparation & storage. Kids Health. November, 2021.
Agustina Fernandez is a medical doctor, who graduated from Universidad Nacional de Cordoba, in Argentina. She has experience working in an emergency room of a public hospital, where she helped many patients with urgent diseases. However, her true passion are children and she is planning on doing her specialization degree in Pediatrics soon. In the past year, she has become interested in researching about infant nutrition, including breastfeeding, infant formula and food in the first years of little ones' lives.
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Dr. Hsu received his medical degree from Tufts University in Boston, Massachusetts, and holds a Master’s of Science degree from both Harvard University and Tufts University.
Dr. Hsu did research in MRI neuroimaging research of fetal brains at Boston Children’s Hospital, an affiliated hospital of Harvard Medical School. Dr. Hsu is currently a full-time medical writer and consultant.
Outside of the medical profession, Dr. Hsu loves to write, learn new languages, and travel