Pregnancy and baby

Making up infant formula

Your baby’s immune system is not as strong or well developed as an adult’s, so babies are much more prone to illness and infection. This means that good hygiene is very important when making up a feed.

All equipment used to feed your baby must be sterilised. Bottles, teats and any other feeding equipment need to be cleaned and sterilised before each feed to reduce the chances of your baby falling sick or getting diarrhoea.

Bacteria in infant formula

Even when tins and packets of powdered infant formula are sealed, they can sometimes contain bacteria such as Cronobacter sakazakii and, more rarely, salmonella. Although these bacteria are very rare, the infections they cause can be life-threatening.

Bacteria multiply very fast at room temperature. Even when the feed is kept in a fridge, bacteria can still survive and multiply, although they do this more slowly.

To reduce the risk of infection, it's best to make up feeds one at a time, as your baby needs them.

Use freshly boiled drinking water from the tap to make up a feed. Don't use artificially softened water or water that has been boiled before.

Leave the water to cool in the kettle for no more than 30 minutes. This will ensure it stays at a temperature of at least 70C. Water at this temperature will kill any harmful bacteria. Remember to let the feed cool a little more before you give it to your baby.

Don't use bottled water when making up formula milk

Bottled water is not recommended for making up feeds, as it's not sterile and may contain too much salt (sodium) or sulphate. If you have to use bottled water to make up a feed, check the label to make sure the sodium (also written as Na) level is less than 200 milligrams (mg) per litre, and the sulphate (also written as SO or SO4) content is not higher than 250mg per litre. It's not usually sterile so, like tap water, it will still need to be boiled before you prepare the feed.

Step-by-step guide to preparing a formula feed

  • Step 1 Fill the kettle with at least 1 litre of fresh tap water (don’t use water that has been boiled before).
  • Step 2 Boil the water. Then leave the water to cool for no more than 30 minutes, so that it remains at a temperature of at least 70C.
  • Step 3 Clean and disinfect the surface you are going to use.
  • Step 4 It’s very important that you wash your hands.
  • Step 5 If you are using a cold-water steriliser, shake off any excess solution from the bottle and the teat, or rinse the bottle with cooled boiled water from the kettle (not tap water).
  • Step 6 Stand the bottle on a clean surface.
  • Step 7 Keep the teat and cap on the upturned lid of the steriliser. Avoid putting them on the work surface.
  • Step 8 Follow the manufacturer’s instructions and pour the amount of water you need into the bottle. Double check that the water level is correct. Always put the water in the bottle first, while it is still hot, before adding the powdered infant formula.
  • Step 9 Loosely fill the scoop with formula, according to the manufacturer’s instructions, and level it off using either the flat edge of a clean, dry knife or the leveller provided. Different tins of formula come with different scoops. Make sure you only use the scoop that is enclosed with the powdered infant formula you are using.
  • Step 10 Holding the edge of the teat, put it on the bottle. Then screw the retaining ring onto the bottle.
  • Step 11 Cover the teat with the cap and shake the bottle until the powder is dissolved.
  • Step 12 It's important to cool the formula so it's not too hot to drink. Do this by holding the bottom half of the bottle under cold running water. Make sure the water does not touch the cap covering the teat.
  • Step 13 Test the temperature of the formula on the inside of your wrist before giving it to your baby. It should be body temperature, which means it should feel warm or cool, but not hot.
  • Step 14 If there is any made-up formula left after a feed, throw it away.

Dos and don'ts of making up infant formula

  • As manufacturers’ instructions vary as to how much water and powder to use, it's important to follow the instructions very carefully.
  • Do not add extra formula powder when making up a feed. This can make your baby constipated and may cause dehydration. Too little powdered infant formula may not provide your baby with enough nourishment.
  • Do not add sugar or cereals to the feed in the bottle.
  • Never warm up infant formula in a microwave, as it can heat the feed unevenly and may burn your baby’s mouth.

More information

Read more about bottle feeding and find the answers to common questions about infant formula.

Page last reviewed: 02/10/2014

Next review due: 02/10/2016


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The 11 comments posted are personal views. Any information they give has not been checked and may not be accurate.

Qqqlp said on 11 October 2015

Hi, i took the trouble to register etc as i keep seeing thisadvice not to heat milk in microwave but it is incorrect. Microwaves do create hot spots but bear in mind milk is a liquid so a quick swirl of the bottle will fix this. It takes about 20s to warm milk in the microwave instead of what can seem like an eternity in warm water whilst your baby is screaming! Lots of things are potentially dangerous or harmful if done carelessly but perfectly safe if done carefully. And none of that nonsense about microwaves harming people or poisoning food/drink is true either. Hope this helps.

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Oldcatlady said on 23 August 2015

Water should be boiled and left to cool for no longer than 30 minutes. That doesn't mean you have to leave it 30 minutes, for those saying they can't make their baby wait 40 minutes for a bottle.
As for it needs to be at least 70? to kill bugs in formula powder, what happens with special "reflux formula" where you can only use warm water?

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lizb87 said on 03 December 2014

It's interesting that my daughter is currently in an NHS hospital but there is apparently no facility for freshly boiled water on the children's ward. She has a formula which isn't available ready made, so I have been instructed by the nurses to make up the feeds with sterile water at room temperature which of course won't kill off any bugs in the powder.

I gave birth to her at the same hospital, where the advice on the maternity ward is to use freshly boiled water to make up feeds and yet a stones throw away on a different ward I get told it's not possible for me to do it!

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Moni777 said on 07 July 2014

Could anyone please, preferably from the NHS, answer the following questions:
1. Can we reheat once boiled water to prepare the powder formula, and if so is it necessary to reheat to 70 degrees?
2. What are the best tips to prepare powder formula for travel? Can we pre-prepare it and store it in a thermal pouch to take away? Or, should we take the boiled water with us instead?
3. Is it safe to dissolve the powder in a pre-boiled water at a temperature ready for feeding? I know some mothers keep the once boiled water in a jug and heat it up only to the temperature ready for feeding...
Please be as honest as possible with your answers rather than recite the official recommendations. I am more interested in what is safe and actually works for mums. My sanity depends on it! Thank you in advance.

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WeenaT said on 29 May 2014

Although this is the safest advice and follows the manufacturers instructions for preparation, this advice does not take into consideration the stresses of new parents. Advising parents that they should be getting up however many times in the night to prepare a fresh night feed and leaving your child to scream and become distressed for 40 minutes+ per feed while you prepare their bottle is ludicrous. The NHS recommend demand feeding as the only way to go and putting your baby through this distress 2, 3, 4+ times per night - you would never get any sleep at all after following this process! The WHO states in their PDF document that if you do need to prepare feeds in advance, you should make them in exactly the same way, boiling the kettle 30 minutes before with 1 litre of water, and adding the milk powder just as you normally would to kill any bacteria in the powder. Cool as quickly as possible and get the feeds into the back of the fridge (the coldest part), using within 24 hours. I always just make mine 12 hours ahead. You just have to ensure that everything is clean, sterilised and sanitary. Nice clean hands and a nice clean fridge.

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parentinged said on 05 April 2014

Hi everyone,

The following excerpt from the WHO guidelines on preparing formula may clarify things.

''Taking care to avoid scalds, pour the correct amount of
boiled water into a cleaned and sterilized feeding bottle.
The water should be no cooler than 70ºC, so do not
leave it for more than 30 minutes after boiling.''


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newmum2h said on 29 April 2012

It is disappointing that after 16 weeks I have stumbled across this page. I had problems with breastfeeding as I had a premature baby and it's such a shame that I returned home from hospital having little clue about the best way to go about sterilising bottles and how to feed my baby breast milk topped up with formula. I even spent ages expressing in hospital to have to throw it away on one occasion as no one had thought to advise me before giving the expressed milk to my child (when he eventually gained the ability to suck), that any feed not taken within an hour had to be discarded. Eventually I began to solely formula feed and I had to rely on the little information I could pull off the internet to help me with this.

Tabouleh's comment that states the water should not be hotter than 70 degrees is inaccurate. The WHO's guidelines only state a minimum temperature (70 degrees). There have been some theories put forward that hotter water can kill nutrients but the advice of the WHO is anything over 70 degrees is fine. The main risk comes from scalding yourself during preparation. A good way of overcoming the problem of powder sticking to the scoop is to put the relevant number of scoops into a powder dispenser and then deposit the powder from this into the bottle.

It's such a shame there is so much confusion and so little support. Ultimately if you get it wrong then babies can become really sick.

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Sue2006 said on 02 October 2011

I don’t believe it is responsible for the NHS guidelines to simply state that all feeds should be made on demand with boiled water cooled in a kettle for 30 minutes as if this is a realistic expectation for all feeds when clearly it is not. For example, it is hardly feasible to follow the model for night feeds when one doesn’t know when the baby will wake - it would require leaving the baby to scream with hunger for 40 minutes or so in the early hours while the parent struggles, half asleep, to prepare their bottle! Also, how about when out about with the baby without access to a kettle?
Furthermore, in following the guidelines myself I have discovered that the steam from the very hot water in the bottles causes the formula to stick quite severely within the scoop and leads to the feeds being accidentally prepared more dilute than they should be.
I think it would be more realistic to explain that according to the latest recommendations the safest way to prepare a feed is as outlined but where this is not feasible the next best alternatives are described (this is actually what the WHO do in their recommendations.)
By failing to offer alternative, more practical methods of preparation, the logical outcome is that new parents, unable to follow the guidelines, will come up with their own methods of formula preparation which could be more risky than the preparation methods of old.

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ox5it said on 14 January 2011

Thanks for your reply Tabouleh. It sounds like you know what you are talking about. I was hoping that someone from NHS Choices would clarify. I was sceptical about a litre of water only reducing to 70 degrees C in 30 minutes, I will test that sometime. However, the advice on the page did not say NOT to use water that is above 70 degrees. The emphasis was all on making sure that the feed was sterlized. From what you say it seems that the instruction should be "Let the water cool for at least x minutes and no more than 30 minutes". X minutes would be the time it takes for the water to cool to a temperature that does not destroy too many of the nutrients in the milk.

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tabouleh said on 11 December 2010

ox5it - Yes the water should be boiled and cooled for THIRTY (30) minutes.

1 litre of water boiled and left to cool for 30 minutes in a normal kettle will be 70 degrees C.

70 degrees C is hot enought to kill the bacteria.

The UK guidelines are based on the World Health Organisation guidelines and there have been a number of research experiments to support these guidelines.

Using water which is hotter than 70 degrees could destroy some of the nutrients in the milk.

I have no idea why NHS Choices published your comment as it contains inaccurate information.

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ox5it said on 04 December 2010

On this page (and in the printed edition from 2009) in relation to making up formula it says "After it's boiled, let the water cool for no more than 30 minutes." Surely this should read '3 minutes'! After 30 minutes the water would be too cool to kill bacteria.

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