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Here we explain how to prepare a bottle for going out and how to make up formula safely when you are out...

When you're making up formula for your baby, you need to be very careful to do it safely and hygienically. Formula powder isn’t sterile, so any bacteria in the powder can grow when the formula is made up. Your baby’s immune system is still not fully developed so they are sensitive to contaminated food and may become very ill if they consume it.

Read about how to make up formula safely here. The same guidelines apply when making up bottles of formula milk when you're out, but more precautions may be needed.

Here's how to prepare to bottle feed your baby formula when you're out...

What is needed for formula feeding when out?

If you need to prepare formula to feed your little one away from home, you'll need to take with you:

  • a measured amount of formula powder in a small, sterile, dry container
  • a vacuum flask of hot water that's just been boiled
  • an empty sterilised feeding bottle with cap and retaining ring in place.

(NHS, 2019a)

The vacuum flask doesn't need to be sterilised but it should be cleaned thoroughly and only used for your baby. Boiling water should kill any bacteria present in the flask. If the flask is full and sealed, the water will stay above 70°C for several hours (NHS, 2019a).

How to prepare a bottle of formula in advance


  • Make up a fresh feed only when your baby needs it. The water must still be above 70°C when you use it, to kill any bacteria that could be present in the formula powder.
  • Remember to cool the bottle (with the lid on) under cold running water. Always test the milk temperature on the inside of your wrist before you feed it to your baby.
  • Alternatively, you could use a carton of ready-to-feed liquid baby formula when you're away from home. This is a convenient but more expensive option. Once open, it will need to be sealed, stored at the back of the fridge and used within 24 hours.
  • To protect your baby from the bacteria that can grow in formula, a fresh feed should be made up when your baby needs it. If this isn't possible, prepare the feed at home, cool it quickly and store it in the back of the fridge for at least one hour. Take the formula out just before you leave, and transport it in a cool bag with an ice pack and use within four hours. Use within two hours if you do not have access to a fridge or cool bag.

(NHS, 2019a,b; Public Health Scotland, 2021)

How long is formula OK for once made?

If you need to make up formula in advance, it should be used within:

  • 24 hours if stored in a fridge
  • four hours in a cool bag with an ice pack
  • two hours at room temperature.

(NHS, 2019a; Public Health Scotland, 2021)

Bacteria can still survive and grow in the fridge or a cool bag, but at a slower rate than at room temperature. The longer the prepared formula is stored for, the greater the risk of infection (NHS, 2019a; Public Health Scotland, 2021).

Can I use bottled water to make up infant formula?

Bottled water is not recommended for making up infant formula feeds for your baby. This is because it's not usually sterile and may contain too much salt (sodium) or sulphate (NHS, 2019a).

If you're abroad and unsure of the water quality, it might be better not to use tap water. In this case you may need to use bottled water. Water that is labelled as 'natural mineral water' may contain too much sodium or sulphate for your baby. So choose still (not sparkling) water, making sure the seal isn’t broken. It will still need to be boiled to make sure it is sterile. Check the label to make sure that:

  • the figure for sodium (also written as Na) is no higher than 200 milligrams (mg) per litre
  • the figure for sulphate (also written as SO or SO4) is less than 250 milligrams (mg) per litre.

Once opened, store the bottled water in a fridge and use within the time recommended on the bottle; for example, it might say ‘use within 3 days’ (Public Health Scotland, 2021).

This page was last reviewed in February 2022.

Further information

NCT supports all parents, however they feed their baby. If you have questions, concerns or need support, call our support line on 0300 330 0700, whether you are using formula milk, breastfeeding or mixed feeding. If you’re concerned about your baby’s health talk to your health visitor or GP.

NHS. (2019a ) Formula milk: common questions. Available at:… [Accessed 13th February 2022]

NHS. (2019b) Types of formula milk. Available at:  [Accessed 13th February 2022]

Public Health Scotland. (2021) Formula feeding: How to feed your baby safely. Available at: [Accessed 13th February 2022]

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