How Long Does Formula Last?

A baby’s immune system is still growing, meaning it is not as strong or developed as an adult’s. This makes babies much more prone to illness and infections, particularly from food-borne germs. Sticking to official guidelines is therefore crucial when making up and storing a feed. Read this article to find out how long formula lasts once made up and other useful information on storing a feed.

How Long Does a Formula Bottle Last at Room Temperature?

Bacteria multiply most rapidly at room temperature. This means the risk of infection increases the longer formula is left sitting out on the counter. Salmonella and Cronobacter sakazakii are the bacteria of greatest concern when it comes to infant formula. Food poisoning caused by these bacteria may cause your child to experience diarrhoea.

Any made-up infant formula that has not been used and has been kept at room temperature must be thrown away within two hours. If there is any unused formula left in the bottle once you’ve finished bottle feeding your baby, it needs to be thrown away. This can help make sure your little one doesn’t experience any tummy aches or other formula-related food poisoning symptoms.


To reduce the risk of infection, make up each feed as your baby needs it. It’s best to use freshly boiled water from the tap (cooled slightly to 70 degrees Celsius or above) to kill any harmful bacteria that may be present. Remember to cool the formula before giving it to your baby.

Importantly, bottled water, artificially softened water or water that has been re-boiled must not be used to prepare infant formula as these forms of water are not sterile and may contain too much sodium or sulphate.


How Long Does Made-Up Formula Last in the Fridge?

While a feed should ideally be made up when needed to reduce the risk of infection, sometimes there isn’t any option but to store a feed. In this case, unused liquid infant formula should always be stored at the back of the fridge for no longer than 24 hours. Even if a feed is kept in the fridge, bacteria can still survive and multiply, although at a slower rate than at room temperature. This means the longer the prepared feed is stored, the greater the risk of infection.

Transporting a Feed

If you need to transport a feed – for example to a nursery or childminder – you should first prepare it at home and cool it at the back of the fridge for at least one hour. Remove the made-up formula from the fridge just before leaving and store it in a cool bag with an ice pack. It then needs to be used within four hours. If you don’t have an ice pack or access to a fridge, the made-up formula must be used within two hours.

Ready-To-Feed Liquid Infant Formula

Alternatively, you may opt to buy ready-made formula in a carton so you don’t need to worry about mixing it when out and about. When using ready-made formula, it’s important that it is prepared and stored following the manufacturer’s instructions. Once ready-made formula cartons are opened, they need to be stored in the fridge either in the carton with the cut corner turned down or in a sterilised container, for no more than 24 hours. As ready-made formula is sterile, it can help reduce the risk of infections. This makes it particularly suitable for high-risk infants, i.e. babies that are pre-term, low-birthweight or particularly vulnerable to infections. Keep in mind that all feeding equipment still needs to be sterilised if you are using ready-to-feed liquid formula.

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Can You Reheat Baby Formula?

According to NHS guidelines, bottles of formula your baby has already started drinking from should never be reheated. Formula should also never be warmed up in a microwave, as this may heat the feed unevenly and burn your little one’s mouth. If you’re out and about and don’t have access to facilities to make your baby a bottle of formula, it may be a good idea to bring a flask of boiling water and make up a feed when required. Use a sterile pot to store your pre-measured powdered milk. When stored in a full 500 ml vacuum flask, boiling water will remain above 70 degrees Celsius for around 3 hours. By comparison, a 1 litre vacuum flask filled with boiling water will keep the water temperature above 70 degrees Celsius for at least 6 hours.


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How Long Does Powdered Formula Last in the Container?

Unopened (powdered) infant formula containers need to be stored in a cool, dry, indoor place like a kitchen cupboard. Once a container has been opened, store in a cool, dry place with the lid tightly closed. Do not store it in the refrigerator. Instructions vary on how long to keep the container once opened. Please check the container to see what the manufacturer advises. Typically, powdered formula will need to be used within one month.


Even when containers of powdered infant formula are sealed, they can still potentially contain harmul bacteria that can make your baby ill. While these bacteria are rare, the infections they cause can have serious effects.

In order to reduce the risk of infection, make sure to properly sterilise feeding equipment before making up a feed and try to avoid storing pre-prepared formula in the fridge for future feeds where possible.



Ideally, each feed should be freshly made when needed. However, if this is not possible, or you want to prepare in advance, unused bottles of formula must be consumed

  • within 2 hours if stored at room temperature
  • within 24 hours if stored in the fridge
  • within 4 hours if stored in a cool bag with an ice pack

The Bottom Line

There are quite a few things to keep in mind when preparing and storing formula, but with a bit of practice, you’ll master this skill in no time. Sticking to the following guidelines can help reduce the risk of infection for your little one. If made-up formula is stored

  • in a fridge – use within 24 hours

  • in a cool bag with an ice pack – use within 4 hours

  • at room temperature – use within 2 hours.

For more information on feeding your child, check out our articles on baby-led weaning and introducing solid foods to your baby.

How We Wrote This Article
The information in this article is based on the expert advice found in trusted medical and government sources, such as the National Health Service (NHS).The content on this page should not replace professional medical advice. Always consult medical professionals for full diagnosis and treatment.

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