How to Prepare Formula Milk: A Step-by-Step Guide

Before you get started, familiarise yourself with the back of pack instructions as some formula milks may differ slightly in how they need to be prepared.

You will need:

Boil fresh tap water

Boil 1 litre of freshly-run tap water and leave to cool for no longer than 30 minutes.
The water that goes into your baby’s formula milk should be fresh – so not water that’s been sitting in the kettle for hours. Also avoid using artificially softened water.

Wash your hands

It’s very important to keep everything as clean as possible, so while the water is cooling, wash your hands and clean and disinfect the bottle preparation area. Make sure your bottle, teat and lid are also clean and have been sterilised.

Measure the right amount of water

Measure the required amount of cooled boiled water into a sterilised bottle, following the feeding guide on the pack. Always pour the water in first so you can use the measuring gauge on the bottle. Below is a rough guide to how much you can expect your baby to drink.

Add the right amount of formula powder

Using the scoop provided, add the required number of scoops of powder – one level scoop of powder for each fluid ounce of water (approx. 30 ml). For example, 5 scoops in 150 ml.cooled boiled water. Level off the powder with the back of a clean dry knife, but don't press the powder down into the scoop. All formula milks have instructions on the packaging to remind you of the correct ratio.

Shake the bottle well

Place the sterilised teat and cap on the bottle and shake well until all the powder has dissolved (approx. 15 seconds).

Cool the milk to the right temperature

Cool the milk to drinking temperature (approximately 37°C) by holding the bottle under cold running water or by placing in a bowl of cold water. ALWAYS test the temperature of the milk before feeding by dripping a bit onto the inside of your wrist; the milk should feel warm, not hot.

For more advice, check out our guide on how to bottle feed your baby.

It’s always best to make up formula as and when you need it, but sometimes you might need to make a bottle in advance. The following advice is for when it’s really necessary, for example when you are not able to take a vacuum flask filled with boiled fresh tap water to make up a feed when you’re out and about, and when to ready to feed formula isn’t an option. We don’t recommend stocking your fridge with premade bottles of formula on a regular basis.

Make up the formula as normal, then store it in the back of the fridge (where it’s coldest) at 5°C or below. Premade formula must be used within 24 hours even when refrigerated. If you’re taking pre-prepared formula out and about, use an ice pack to keep it cool and use within 4 hours. If formula is left at room temperature, it should be consumed within 2 hours.

If your baby has started a bottle and not finished it, these rules don’t apply – leftover formula should always be thrown away.

The advice on using formula feeds outside of the home differs in Ireland – please refer to the HSE website for further information: Bottle feeds when you're away from home .

If your little one falls asleep while you’re preparing their milk, or you get sidetracked between making and feeding by a nappy explosion (it happens!), that bottle of formula milk should be ok to drink for up to 2 hours if left at room temperature. If a bottle is started and abandoned, however, it should be discarded. Check out all our formula milk FAQs for more guidance.