Preparing and sterilising bottles: the safe method, step by step

Bottle-feeding comes with its own little ritual, and at 3 a.m. it can feel like a lot to remember. Good news: the safe routine is short and quickly becomes second nature. Wash, sterilise, make up fresh — three steps that protect a tiny tummy whose defences are still developing. Here is the method, calmly and in order, so feeding time stays a moment of closeness rather than a source of worry.

Start with clean hands and a clean surface

Before you touch a single bottle, wash your hands with soap and water, and give the worktop a quick clean. It sounds obvious, but it is the first line of defence: your hands and the surface are where stray germs hitch a ride. A clean, dry space, a clean cloth, and you are ready. This tiny habit, repeated before every preparation, does a surprising amount of the work.

Wash first — sterilising doesn't clean

Sterilising only works on equipment that is already clean, so washing always comes first. As soon as a feed is finished, take everything apart: bottle, teat, ring, cap. Wash each piece in hot soapy water with a bottle brush, paying attention to the teat, where milk loves to hide — squeeze water through the hole to clear it. Then rinse thoroughly. A hot dishwasher cycle is a fine alternative for the washing step, though it does not replace sterilising. Whichever you choose, the goal is the same: no milk residue left behind.

Sterilising: keep it up for the first year

Because a baby's immune defences are still immature, sterilising all feeding equipment is recommended for the first 12 months. Pick the method that suits your home: an electric or microwave steam steriliser, boiling for 10 minutes in a large pan (make sure everything stays under water), or a cold-water sterilising solution. They all do the job well. One helpful habit: leave the clean items inside the steriliser until you need them, so they stay protected. If you take a bottle out and won't use it straight away, it is worth putting it back together fully — teat, ring and cap on — to keep the inside clean.

Making up a formula bottle safely

Here is the step most parents don't hear about: powdered formula is not sterile. That is why the water matters. Boil fresh water, then let it cool for no more than about 30 minutes so it is still at around 70 °C — hot enough to kill any bacteria that might be in the powder (such as Cronobacter), which is exactly why you don't let it cool further first. Pour the measured water into the bottle first, then add the powder using the scoop that came with the tin: levelled off, never packed down or heaped. Put the teat and cap on, and swirl or shake to mix.

Then cool it back down quickly: hold the bottle under cold running water (keeping the cap area out of the stream) until it feels lukewarm. Test a few drops on the inside of your wrist — it should feel warm, not hot. And whenever you can, make each bottle up fresh, at feeding time.

Fresh every feed — and never the microwave

Formula is best made up for each feed rather than in advance, because warm milk is a comfortable home for bacteria. If your baby doesn't finish a bottle, throw away what's left within an hour or two rather than saving it for later. And skip the microwave entirely for warming: it heats unevenly and creates hot spots that can scald a mouth even when the bottle feels cool. To warm a feed, stand the bottle in a jug of warm water or use a bottle warmer, then test on your wrist again. Simple, safe, done.

Also worth reading: Expressing and storing breast milk: the practical guide · Burping your baby: gentle, effective techniques

This article is for information only and has been reviewed by the Mama4care team. It does not replace medical advice: for any question about your health or your baby's, talk to your midwife, doctor or paediatrician. In an emergency, call your local emergency number.