Powdered infant formula is not a sterile product, which is why every national guideline spends most of its words on cleaning, water and timing rather than on brands. The steps that matter are washing and sterilising the bottle and teat, making feeds one at a time, following the manufacturer's instructions on the tin exactly, and cooling the feed before it is given. This page is health information for learning and it is not medical advice about your baby. How much your own baby needs, and any concern about feeding, belongs with a midwife, health visitor or doctor.
Why preparation matters at all
WHO's guidance on powdered infant formula exists because the powder can contain bacteria even when the tin is sealed and handled properly. CDC names Cronobacter as the organism of concern, and says infections are rare but serious in babies.
The risk is highest for the youngest babies. CDC advises extra care for babies under two months old, babies born before 37 weeks, and babies with a weakened immune system.
Cleaning and sterilising
NHS guidance is to sterilise bottles and teats until a baby is at least a year old, and to wash hands thoroughly before handling anything sterilised.
Wash bottles and teats in hot soapy water with a bottle brush first, then sterilise by the method you have chosen: cold-water sterilising solution, steam, or boiling. Follow the instructions that came with the steriliser.
Check teats regularly and replace any that are damaged, and screw the ring on firmly so the teat cannot come off during a feed.
Making up a feed
Make feeds one at a time, when they are needed, rather than in a batch for later.
Both NHS and WHO guidance say powdered formula should be mixed with water that is still hot enough to kill bacteria in the powder — at least 70C — which in practice means freshly boiled water left to cool for no more than half an hour. Water goes in the bottle first, then the powder.
Follow the scoop and water instructions on your tin exactly, because they differ between products. Guidance is clear that adding extra powder or extra water is unsafe, and that sugar or cereal is never added to a bottle.
Cool the made-up feed before giving it, by holding the closed bottle under cold running water, and test the temperature on the inside of your wrist. It should feel warm, not hot.
Where countries differ
This is one of the places where national guidance genuinely does not agree, so follow the advice published where you live.
NHS guidance applies the hot-water method to every feed for every baby. CDC guidance says that most of the time it is safe to prepare powdered formula with safe tap water following the label instructions, and reserves boiled water for babies at higher risk, for emergencies, and where water safety is uncertain.
If your water supply is not safe to drink, or there is a local advisory, CDC advises bottled water or ready-to-feed formula until authorities say tap water is safe again.
Storing and throwing away
CDC guidance says prepared formula should be used within two hours of preparation, and within one hour of a feed starting. If it is not going to be used within two hours, it goes straight in the fridge and is used within a day.
Any formula left in the bottle after a feed is thrown away rather than saved. NHS guidance also advises against warming feeds in a microwave, because it heats unevenly and creates hot patches.
Giving the feed
Hold your baby close and fairly upright, with their head supported so they can breathe and swallow comfortably. Brush the teat against the lips and let your baby draw it in.
Keep the bottle roughly horizontal, only slightly tipped, so milk flows steadily rather than fast. Give your baby time, and pauses.
Never prop a bottle up and leave a baby to feed alone, and never leave a baby in bed with a bottle. NHS guidance names both as a choking risk.
Follow your baby rather than the bottle. NHS guidance says babies take different amounts at different feeds, and that a baby does not have to finish a bottle. Feeding your newborn covers cues and what clinicians look at.
If you are combining breast and bottle
Many families do both, permanently or for a while. Support is worth asking for early, whichever direction you are moving in.
When breastfeeding is not working covers the decision, the practicalities and the feelings that come with it.
When to see a doctor
Seek urgent care for any sign in the box below, and for a baby who refuses feeds, vomits forcefully after every feed, or has far fewer wet nappies.
Ask a midwife, health visitor or doctor about feeds that are consistently distressing, about a baby who is very unsettled after feeds, and about any change of formula, which is a clinical decision rather than a shopping one. Your newborn in the first two weeks sets out what is usual, and newborn warning signs sets out what is not.
Seek care now: Contact your local emergency services or go to your nearest emergency department if a baby under three months old has a temperature of 38C or higher, is breathing fast, working hard to breathe or grunting, has blue, grey, pale or mottled skin, is floppy, is difficult to wake, is refusing feeds, has far fewer wet nappies or none in the past 12 hours, has a bulging or sunken soft spot on the head, has a rash that does not fade when you press it, or has a fit. Femio cannot assess a baby.
Frequently asked questions
Can I make up bottles in advance for the night?
Guidance is to make feeds one at a time as they are needed. Ask your midwife or health visitor how to manage night feeds safely with the guidance where you live.
Do I have to sterilise, or is washing enough?
NHS guidance says sterilise bottles and teats until your baby is at least a year old, after washing them in hot soapy water.
How much formula does my baby need?
Follow the instructions on the tin, and ask a midwife or health visitor about your own baby. No page and no app can set that for you.
Is one brand of formula better?
Talk to a health visitor or doctor rather than comparing tins. First infant formula is regulated, and any change for a medical reason is a clinician's decision.