What Happens If Baby Accidentally Drinks old Formula

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Feeding a baby at night is exhausting. And out of exhaustion, if you have given your baby an old formula sitting on a table since the last feed, you might be worried. So here is what you need to know if your baby accidentally drinks old formula.

Whether your baby is formula-fed or breastfed, feeding the baby at night can be exhausting. And I don’t blame you if you feel too lazy to wake up and make a new bottle of formula in the middle of the night on one of those days.

And realizing that you have given your baby an old formula bottle, sitting on your night table from the last feed, can be the worst feeling in the morning. And you may start questioning yourself,

Did I poison my baby? What will happen to my baby? Is my baby okay?

Baby drinking bottle - Baby accidentally drinks old formula

Before you drown in guilt, take solace in knowing that your baby is probably okay. Babies are not that fragile. The worst thing that can happen to your baby is food poisoning. You may want to watch your baby for vomiting, diarrhea, and fever for two days. If they develop the symptoms, you need to contact your pediatrician immediately.

Now, let’s look at what happens if a baby accidentally drinks old formula and what you need to do.

What is Old Formula?

Just like breastfeeding, formula feeding has its challenges. For example, handling the formula, preparing and sterilizing the bottle, and teaching the baby to drink from it have their own challenges.

And when you think everything is sorted with bottle feeding, the baby suddenly starts rejecting or refusing to drink the formula, or the baby squirms and cries while bottle feeding.

The most challenging part of formula feeding is preparing a fresh bottle of formula for each feeding session. It gets really challenging when you get out of bed to prepare the formula bottle to feed your baby.

can with expiration date

This is because the shelf life of the prepared formula is very short. According to CDC, prepared infant formula should be used within 2 hours of preparation and within one hour from when feeding begins.

Prepared formula (not given to baby) should be stored in the refrigerator and used within 24 hours.

The prepared formula sitting at room temperature for more than 2 hours should be considered old. Any leftover formula the baby did not finish should be discarded after 1 hour as there are higher chances of bacteria growing in this old formula.

Formula powder or liquid formula that is passed the expiration date is also considered old formula. So, if you have spare formula powder sitting at the back of the cabinet, check the expiry date before giving it to your baby.

Also, the powdered formula should be used up within one month. Leftover past one month of opening the can should not be given to a baby.

What causes the formula to go bad after 1 hour or 2 hours at room temperature?

According to CDC, the prepared formula should be used within 1 hour if the baby has drank it, or freshly prepared formula should be used within 2 hours if stored at room temperature.

two baby bottle besides red bucket
Photo by Jaye Haych on Unsplash

Once the baby drinks the formula and saliva mixes with the formula, it becomes a breeding ground for the bacteria. And when you store leftover formula at room temperature, it becomes a favorable environment for bacteria to grow.

So, the leftover formula from the last feed should be discarded within 1 hour.

In addition, if you have prepared the formula and it is sitting at room temperature, it is unusable after two hours. But, again, this is mainly because of the stability of the product.

Infant powdered formula is made by deep modification of cow milk to mimic breast milk composition for formula-fed newborns’ proper neural and cognitive development.

In particular, milk-based formulas are supplemented with polyunsaturated fatty acids – linoleic, arachidonic, and docosahexaenoic acid.

And the problem with fats and oil-containing food is their autoxidation process. So they start deteriorating when they are exposed to air.

So, if stored at room temperature for a long time, the unused prepared formula will change its flavor and odors.

Therefore, if you are not going to use the prepared formula immediately, refrigerate it. Refrigeration slows the process of autoxidation, and according to CDC, you can use the refrigerated formula for up to 24 hours.

But it is best to discard the formula within one hour once the baby’s saliva is mixed into the bottle as bacteria is already introduced through saliva.

What happens if a Baby accidentally drinks Old Formula?

Caring for a baby 24/7 is not an easy job. And if your baby accidentally drank old formula, do not panic. Accident happens! We all make mistakes.

It is unlikely that your baby will be fatally ill if you accidentally fed your baby old or expired formula. But just like you get sick after consuming spoiled food, your baby may show symptoms of food poisoning.

Here are the symptoms that you need to watch out for.


Vomiting is the most common symptom when you have eaten something spoiled. And because infants’ immune system is still immature, anything that is of not optimal quality, including old formula or formula that sat at room temperature for a long time, can make a baby sick. 

You may need to call the doctor if vomiting persists long with diarrhea for more than 12 hours to avoid the risk of dehydration.


Because of a baby’s immature immune system, the old formula can upset the baby’s stomach and cause diarrhea.

Watch out for their diaper output. Baby’s poop is usually loose, but if you see frequent diaper changes and loose poop than normal, it may indicate that your baby has diarrhea.

Contact your pediatrician if your baby has diarrhea and vomiting after drinking old formula.


Dehydration follows diarrhea and vomiting. Infants who lose so much body fluid because of diarrhea and vomiting cannot maintain their normal body function.

The symptoms of dehydration include,

  • Fewer wet diapers
  • Dry tongue and lips
  • Rapid breathing
  • Tearless crying
  • Baby looks lethargic

What happens if a Baby Drinks an Old Bottle of prepared Formula?

Once the formula is mixed with water, it has to be utilized within two hours if the bottle is left at room temperature. This is because bacteria can grow in the prepared formula if the bottle sits at room temperature.

The biggest risk of a baby drinking an old bottle of prepared formula is symptoms of food poisoning. Your baby may develop vomiting and diarrhea that can lead to dehydration if the symptoms are treated quickly.

If your baby shows any sign of food poisoning, talk to your pediatrician immediately.

How can you tell if Formula has gone Bad?

The powdered formula is good for one month after opening the seal. However, once the powdered formula is exposed to air, it must be utilized within one month.

If your baby is formula fed, then the can of powdered formula will not last one month. But if you purchase the powdered formula in bulk, it is possible that a can of unopened formula sitting at the back of your closet may pass the expiry date.

But an open can of formula go bad if you do not follow good hygiene practices while preparing a bottle for your baby. But you can always do the following tests to see if the formula has gone bad.

The powdered formula may look clumpy

Sometimes powdered formula looks clumpy if moisture has been introduced in the formula can.

women putting formula powder in a baby bottle

If you see clumps in your powdered formula, it means that formula is not good for your baby. This usually happens when multiple people are involved in preparing the formula.

For example, handling a formula spoon with wet hands could introduce moisture to the formula can.

The prepared formula may have a foul smell

If the formula has gone bad, the prepared formula will smell ‘off.’ However, you won’t notice it until you smell the prepared formula. So, if you suspect the formula may not be good, you want to smell the prepared formula before giving it to your baby.

The prepared Formula tastes sour

I always like to do smell and taste tests when I doubt the quality of formula milk or breast milk.

When the formula is expired or old, it will change its taste due to the oxidation process and may taste sour when you taste it.

Usually, you do not taste formula before giving it to the baby, but when in doubt, trying formula before giving it to your baby will save you from guilt later.

Prepared formula ingredient separation

Another indication of the old or expired formula is formula ingredient separation after mixing with water.

If your prepared formula ingredients separate and you have difficulty mixing it, it indicates that the formula may have gone bad.

Change in baby’s Behavior

After feeding your baby formula, if she shows sing of uneasiness or develops symptoms of food poisoning – vomiting, diarrhea, or getting sick, it may indicate that baby has drank spoiled formula or milk.

What do you do if the Baby drinks old Formula?

If you have accidentally given your baby prepared formula that has been sitting at room temperature for longer than two hours, a leftover formula that has been sitting at room temperature longer than 1 hour, or powdered formula can that is open for longer than 1 month, and have found out just now, you likely have a panic attack.

It is natural for moms to panic as we want the best for our babies. But don’t feel bad about yourself. Mistake happens, and this is what you should do if your baby drank old formula or expired formula,

Don’t Panic, and Stay Calm

Let me tell you; you are not the first mom who accidentally gave your baby an old formula.

Caring for a baby is not easy, and mistakes are unavoidable when you have sleepless nights in the first few months. But, as long as these mistakes are not life-threatening, don’t beat yourself up!

We all learn from our mistakes, so don’t panic and stay calm.

Keep a close eye on your baby’s health

Once you find out that you have accidentally given your baby old formula, you want to keep a close eye on the health of your baby.

If you see your baby uneasy after feeding, she may have discomfort in her stomach because of old formula or expired formula.

Your baby may develop a fever, so check their temperature every couple hours. If they have a fever, talk to your pediatrician.

Your baby may start symptoms of food poisoning. If they start throwing up or have diarrhea, you want to watch your baby closely.

Keep track of how often they are vomiting and count their diaper output. If it is frequently happening, you need to talk to your pediatrician.

Keep your baby hydrated

If your baby is vomiting or has diarrhea, it is important to hydrate them frequently. Depending on your baby’s age, you can offer them frequent feed or liquid to make up for the lost fluid.

Dehydration can be dangerous for infants, so you do not want to wait to seek medical help if your baby develops diarrhea.

What to do with expired or old formulas?

If you accidentally gave your baby old or expired formula, toss the can of powdered formula so the mistake does not happen again. You also want to follow CDC guidelines on formula storage for your baby’s safety.

The prepared unused formula can be used within 24 hours if stored in a refrigerator. However, if the prepared formula is stored at room temperature, it should be consumed within 2 hours.

And leftover formula from the feed should be discarded within an hour as there are high chances of bacterial growth after the baby’s saliva mixes with the formula.

Formulas are expensive, and if you have to toss the can of powdered formula because it was sitting in the back of your closet and now it is expired, it can be heartbreaking. But for the sake of your baby’s health, it is best to buy a new can of powdered formula.

If you have an unopened or opened can of formula that has not been used within 1 month, you can use it for other purposes other than feeding your baby.

Here are things you can do with expired or old formula that is not good for feeding your baby but good enough for other purposes,

  • Use expired formula powder to make milk baths for your baby or yourself. Nutrients in the formula will help nourish your baby’s skin.
  • Use the powdered formula for cooking purposes. For example, use formula powder for cooking and baking instead of milk powder. It will add nutrients to your dish.
  • Donate expired formula powder to the animal center.

To find out other uses of expired formulas other than dumping, check out this post on the best uses of expired or old formulas.

Conclusion : Baby Accidentally drinks Old Formula

It is normal to panic when you find out that your baby accidentally drank old formula. But don’t drown yourself in guilt. Mistake happens, and as long as the mistake is not life-threatening, you can forgive yourself.

The main risk of giving a baby expired/old formula is that the old formula may not have enough nutrients that the baby needs to thrive. So, if you have given old formula to your baby, feed them again after 1 hour to make up for the nutrition deficit.

Also, you want to keep a close eye on your baby in case they develop any symptoms of food poisoning. For example, they seek medical attention if they feel uneasy after feeding, start vomiting or have diarrhea.

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