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What Happens If My Baby Drinks Old Formula?

There is a lot to remember when it comes to looking after a baby. When did I last change her diaper? Has she napped yet today? When did she last have some milk?

When you are sleep-deprived and exhausted from the night feeds, you can be forgiven for making a few mistakes now and then when it comes to keeping on track of all your baby care duties.

One mistake some parents make when it comes to formula feeding is feeding their baby a bottle of old formula.

But what happens if a baby drinks old formula?

The good news is, in many cases, nothing serious will happen. In this article we will talk about why old baby formula can be dangerous and what you need to do if you accidentally feed your baby an old bottle of formula. 

What Is ‘Old Formula’?

Bottle feeding is not always as straightforward as it may seem. Parents need to read the preparation guidelines properly and make sure they are mixing the correct amount of powder and water to make their baby’s feed.

It is best to use the prepared formula within an hour, two hours max. Prepared milk can be stored in the refrigerator for 24 hours but should be thrown away if it has not been used within this timeframe.

If a bottle of formula has been left out at room temperature for longer than two hours, this milk is now considered old formula and parents should avoid feeding it to their baby. 

Old formula can also be expired liquid or powder formula that has been prepared correctly and fed to your baby within the correct timeframe. Using expired formula may seem like the most economical option.

No one likes to throw away food and formula milk is expensive – but it is not a safe way to feed your baby. Formula milk comes with an expiration date on the packaging and powdered formula should be used within a month of opening. 

Why Does Baby Formula Go Bad After An Hour?

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While the best and safest way to feed your baby formula is to give them their bottle as soon as it has been prepared, many parents give their baby their formula a little while after it has been mixed.

Whilst baby formula doesn’t immediately turn bad after an hour, bacteria does begin to grow and the feed will become more dangerous for your baby as time progresses. 

Baby formula can go bad if it is left out at room temperature as bottles of prepared formula need to be stored correctly in the fridge for no longer than 24 hours.

If a bottle has been left out at room temperature for an hour and has not been touched, it needs to be tipped away. Also, if your baby has drunk some of the bottles, it is only safe to keep the remaining formula for a maximum of two hours.

It is not safe to feed your baby the formula after two hours as the mixture of the spoiled milk and your baby’s saliva can cause harmful bacteria to grow. 

How Can You Tell If Formula Has Gone Bad?

Sometimes through the haze of sleep deprivation, our tired mom brains struggle to remember every detail of our busy parenting day. You might be staring at that bottle on the kitchen counter and can’t for the life of you remember when you made it.

Or perhaps there’s an unfortunate rip or stain on your formula packaging and you can’t see the expiration date. Sometimes knowing if your baby’s formula is off or not is easier said than done. 

It is always best to err on the side of caution if you are not sure about the safety of your baby’s feed. However, there are a few ways you can tell if formula is spoiled or has gone bad: 

The milk will smell ‘off

Just like when regular cow’s milk has gone bad and has a nasty smell, the same goes for formula. It won’t have the exact aroma of spoiled cow’s milk but you will notice that it smells different from how it is supposed to.


If the formula powder clumps together in the tub or when mixed with water, it’s safe to say that your baby shouldn’t be drinking it.

Separation of formula ingredients

If your baby’s milk starts to separate and you are struggling to mix the milk together properly, the formula is likely expired and whatever you have left needs to go in the trash. 

Your baby gets poorly after feeds

If your baby is normally fine after feeds but has started getting sick and having diarrhea after their bottle, there’s a good chance that the milk has spoiled.

What Happens If My Baby Drinks Old Formula?

We all make mistakes sometimes and it does not make you a bad parent if you have accidentally fed your baby a bottle of old formula. Firstly, try not to panic. It is very rare that babies get fatally sick from drinking the odd bottle of spoiled milk.

However, old formula can make your baby poorly and there are some symptoms of drinking spoiled formula milk that you should be aware of.

Formula milk is a perishable food source and like many other foods, if ‘gone off’ it can cause food poisoning due to the growth of harmful germs and bacteria.

Here is a list of some of the things that may happen if your baby drinks old formula.


A bottle of spoiled formula can upset your baby’s tummy. You may notice their diapers are full of looser than normal poop and they may need changing more frequently.

It is important to keep your baby hydrated if they have diarrhea and to seek medical advice if it doesn’t pass quickly. 


Your baby may be sick after drinking old formula. Whilst seeing your baby vomit is not a nice experience, it is a good thing as it means your baby’s stomach is rejecting the spoiled milk and they are getting it out of their system.

Again, if the vomiting is persistent then you must seek medical attention.


If your baby is being sick and experiencing diarrhea, they run the risk of becoming dehydrated. If your baby stops having wet diapers and seems lethargic and is running a fever, they may be dehydrated.

If your baby continues to vomit and they are still not wetting their diapers after you have given them fluids, you may be in an emergency situation and you need to get professional medical assistance as soon as possible.

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What Happens If My Baby Drinks Expired Powdered Formula Or Expired Liquid Formula? 

It is not just spoiled prepared powdered formula that can cause your baby to become ill. Drinking powdered formula or liquid formula that is past its expiration date is also risky. 

You wouldn’t drink regular cow’s milk that has expired, would you? The same goes for baby formula. However, the risk of drinking previously unopened liquid formula or powdered formula that has expired is less about foodborne illnesses and more to do with the nutrients. 

The vitamins and nutrients in formula milk begin to break down over time. By feeding your baby expired formula milk, you risk your baby becoming deficient in the vital nutrients and vitamins that they need to grow, develop and be healthy.

The odd bottle of expired formula milk is unlikely to make your child ill but when fed to your baby regularly, expired formula can have a dangerous impact on your baby’s development and overall health. 

What Do I Do If I Feed My Baby Old Formula? 

Ok, you have accidentally given your baby a bottle of formula after two hours or the powder has expired and you have only just noticed. Firstly, don’t panic. We all make parenting mistakes sometimes, try not to beat yourself up.

Here are a few things you need to do if your baby drinks old formula:

Stay calm

Take a breath and try to remain calm. Unless your baby seems extremely unwell, this will just end up being one of those parenting mistakes that teach you a valuable lesson.

You will likely become more vigilant when it comes to your baby’s feeds and that is not a bad thing. Relax, you’re not the first mom to feed off formula to her baby and you won’t be the last. 

Watch your baby closely

If your baby starts vomiting or having diarrhea keep a very close eye on them. Monitor how often they are vomiting and having an upset stomach, if it is happening frequently and not improving over time, seek medical advice.

It is also important to keep a note of your baby’s temperature, a fever can be dangerous for young children and if you notice your child has a persistent high temperature, it is time to get some help.

The vomiting and diarrhea are your baby’s body’s way of trying to flush out the germs and bacteria from the food poisoning, it is normal but can be serious if it is continuous and persistent. 

Keep your baby hydrated

Sickness and diarrhea can cause dehydration. It is important that you replenish the fluids your baby is is loosing by offering them drinks regularly. It will depend on your baby’s age what drinks you offer them, if you are unsure seek medical advice.

Dehydration can be extremely dangerous and if your baby is becoming more and more unwell you will need to call for medical assistance. 

Toss all the old formula and expired formula away

You made a mistake, it’s ok, but now you need to make sure it doesn’t happen again. If you have a big tub of expired formula in the cupboard, it needs to go in the trash.

Yes, formula is expensive and it is heartbreaking to throw it away but your baby’s health is the most important thing, right?

In the future, label your prepared bottles if you are storing them in the refrigerator and note down the time you prepare feeds and your baby starts their bottle, that way you will always know if the bottle you have left out on the side is safe to drink or not. 

The Final Thought 

When done correctly, bottle feeding is a safe and easy way to feed your baby and provide them with the vitamins and nutrients they need to grow and develop.

However, feeding a baby old formula can be detrimental to their health and in some cases, cause food poisoning and severe illness.

It is important to remain calm if your baby has drunk an old bottle and to be aware of all the side effects of drinking spoiled formula that has been highlighted in this article. 

It is unlikely your baby will become severely ill from the odd bottle of spoiled formula every once in a while. However, do not be afraid to seek professional medical advice if you are worried about your baby after accidentally feeding them old or expired formula. 

Medical Disclaimer. All content and media on the MomInformed Website is created and published online for informational purposes only. It is not intended to be a substitute for professional medical advice and should not be relied on as health or personal advice.