While it's important to sterilise your baby bottles correctly, you also need to know how to make them up right, too.


It used to be common practice to make up a whole day's feeds in advance and store them in the fridge.

But because of the higher risk of contamination with salmonella and other bacteria in made-up bottles, the NHS now advises that all feeds are made freshly.

Even when tins or packets of formula are sealed, they can still contain bacteria (cronobacter, sakazakii and, more rarely, salmonella) so using boiled water above a certain temperature to make up your bottles is about killing any bacteria in the formula as well as making sure the water you use is sterile.

Now, we have to say, throughout our MadeForMums community there seems to be a lot of confusion about exactly how to make up a baby bottle correctly — and even among our team, our mums did things very differently.

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Dani G, for example, tells us that for night feeds she'd use cooled water from the kettle that had been boiled before she went to bed.

Tara B says she would always boil the water whatever time of night her baby needed feeding, added it to the formula then cooled the bottle in a bowl of cold water: she remembers it took ages to reach drinking temperature for her baby but she did it because: "I just wanted to make sure I followed instructions exactly".


And another of our mums, who has older children, says she always made bottles up in advance (before guidelines changed) and her children never had any issues.

So - how do you make up a bottle?

One member of our MadeForMums community, Sam, asked: "Can you tell me how to make up a bottle safely but so that I can feed her instantly rather than having to wait for the boiled water to cool for 30 mins?

"She doesn't want it too warm. I know a little about preparing the water beforehand, but not sure about that either!"

We do get that it can be tricky — particularly at night — when you need to make up a bottle and have a hungry baby, but NHS guidelines advise that it's best to make up each bottle as you need it and also mention letting the water stand for up to 30 minutes to cool. They say you should:

  • Use tap water (not bottled or filtered water) that hasn't been boiled previously as this can change its mineral content
  • That you leave it for 30 minutes maximum in the kettle after it's boiled to let it cool (no longer as it needs to be at a temperature of 70C or more so that it's hot enough to to kill any bacteria that might be in the formula powder)
  • Then follow the instructions for adding the formula and the water, attach the cap and teat firmly and shake well to fully dissolve the powder
  • Test the temperature of the milk by shaking a little onto your wrist - it should feel slightly warm but not hot
  • Cool the bottle more if you need to - you can stand it in a bowl of cold water or put it under a cold running tap.

Vitally important too, is that you throw away any formula that's not used once you've finished a feed, every time, as made-up feeds offer the perfect environment for bacteria to grow in.

As well as the fact you need the water to cool so your baby can drink the formula safely, some of our mums wonder if there's another reason you need to wait to mix the water with the formula.

Mum Liz, another member of our MadeForMums community says: "As far as I know the reason they tell us to wait 30 minutes is so that the water is hot enough to kill the bacteria but not so hot that it kills off some of the nutrients in the milk."

We asked our trusted GP Dr Philippa Kaye about this one, and she told us: "The water needs to be 70 degrees Celsius or above to kill any potential bacteria in the formula — it says 70 degrees or above and I cannot find any information to say it would be harmful to the formula if hotter."


"Handling boiling water straight out of the kettle, while sleep deprived and counting scoops perhaps is a risk of scalds which may be one of the reasons.

"It may also be that using boiling water directly onto the plastic bottles could increase the amount of the chemical Bisphenol A into the feed from the plastic (though many bottles are now BPA-free)."

Is it OK to take out a flask of pre-boiled water and use that to make up bottles?

We know a lot of our mums take pre-boiled water out in flasks with them to make bottles up when they're on the go — like member of our MadeForMums community Debra, who told us:

"When we're out I take a flask of hot water and the milk is measured out in to the containers that go inside the bottle."

And the good news is — this is fine, as long as you do it correctly. Professor of Paediatric Nutrition Mary Fewtrell, a childcare expert from University College London, told us: "To make feeds outside the home, pour water within 30 minutes of boiling into a vacuum flask to make feeds in a sterilised bottle when needed.

"As long as the boiled water is put into the thermos flask within 30 minutes, and the thermos flask is effective, then it is OK."

Can I make bottles up in advance?

It's a big question — and we'll say it again, current NHS guidelines state that it's best to make up a fresh bottle every time you feed your baby.

However, while WHO (World Health Organisation) guidelines concur that a fresh feed is the best option, they also offer advice on what to do if making a fresh feed isn't possible. Their advice is to:

  • Prep your bottle as normal, following instructions
  • Cool it quickly in cold water
  • Put it in the fridge (no higher than 5 degrees)
  • Use it within 24 hours.

Using ready-made cartons at night, when you're out — or if you have a preemie

Ready-made up formula might not be for everyone: it's quite wasteful in terms of packaging, and can be pricey — but there's no doubt they're convenient and could well come in handy for the odd night feed or day out.

Carol, a member of our MadeForMums community, told us: "Those ready made cartons are more expensive, but are great when out and about as they don't need to be refrigerated until opened and then can be used within 24 hours."

And fellow member of our MadeForMums community Liz says: "Definitely cartons! We use powder most of the time…but you can't beat cartons for instant food! Just keep a sterilised bottle in the fridge."

And in fact, Professor Fewtrell told us she would recommend using ready-to-feed formula for babies with weak immune systems or who are compromised for any reason, for example premature babies — as this formula is sterile.

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Tara BreathnachContent Editor and Social Media Producer

Tara is mum to 1 daughter, Bodhi Rae, and has worked as Content Editor and Social Media Producer at MadeForMums since 2015