Preparing baby formula
Powdered infant formula is not sterile. This means you need to be careful when you're preparing a bottle for your baby. By following these steps you can reduce the risk of making your baby sick.
Breast milk is the best and most natural food for your baby. If you decide to formula feed, it is important that you always prepare your baby's bottle feeds safely.
What you need
To prepare formula milk correctly, you will need:
- a clean work surface
- at least 6 bottles, lids, discs and teats
- formula milk
- a safe water supply
- a kettle
- a bottle brush and a small teat brush
- sterilising equipment like a chemical, steam or microwave kit
- tongs to help you grip the equipment while sterilising
If you have a visual impairment, use wide-necked bottles. They are easier to fill.
You can use boiling water, a chemical steriliser or a steam kit to sterilise equipment.
A steam steriliser is the best. You can get plug-in or microwaveable sterilisers too.
How to make up a formula feed
- Empty your kettle and fill it with 1 litre of freshly-drawn cold tap water and boil. Alternatively, boil 1 litre of water in a clean pan.
- Leave the boiled water to cool in the kettle or pan. Cool it for 30 minutes, but no longer. This will make sure that the water is not too hot, but also that it is no less than 70°C.
- Clean the work surface well. Wash your hands with soap and warm water and dry them on a clean towel.
- Read the instructions on the formula’s label carefully to find out how much water and powder you need.
- Pour the correct amount of water into a sterilised bottle. Water that is 70°C is still hot enough to scald, so be careful.
- Add the exact amount of formula to the boiled water using the clean scoop provided. Reseal the packaging to protect it from germs and moisture. Adding too much or too little formula could make your baby sick.
- Screw the bottle lid tightly and shake well to mix the contents.
- To cool the feed quickly, hold the bottle under cold running water or place it in a large bowl of cold water. Make sure that the cold water does not reach above the neck of the bottle.
- To check the feed is not too hot, shake the bottle and place a drop of liquid on the inside of the wrist – it should feel lukewarm, not hot. Feed your baby.
- Throw away any feed that your baby has not taken within two hours. If your baby is a slow feeder use a fresh feed after two hours.
- After a feed, clean and rinse the bottle and teat.
You may need to use bottled water to make up feeds:
- if you have a water softener system
- have been told to boil all tap water before use
- are on holiday abroad.
How to use bottled water:
- use still water only, never fizzy or sparkling water
- always boil the bottled water before using it to make up feeds
- it is best not to use bottled water labelled as ‘natural mineral water’ as it can have higher levels of sodium and other minerals. It can be used if no other water is available, for as short a time as possible, as it is important to keep babies hydrated.
The Food Safety Authority of Ireland (FSAI) does not recommend the use of formula preparation machines or automatic machines. There is not enough research to show these machines are safe and effective for preparing your baby's bottle.
How much formula your baby needs
This table is a guide only. Talk to your public health nurse or GP if your baby is taking a lot less or a lot more formula than the amounts in this table.
Never re-use leftover milk once your baby finishes feeding. Throw the milk away after two hours.
Your baby's age
Number of feeds
Amount of formula feed per baby weight
Birth to 3 months
6 to 8 (feeding every 3 to 4 hours)
150ml per kilogram (kg)
2½ fluid oz (ounces) per lb (pound)
4 to 6 months
4 to 6 (feeding every 4 to 6 hours)
150ml per kilogram (kg)
2.5 fluid oz (ounces) per lb (pound)
Breastfed and formula-fed babies need 5 micrograms of a vitamin D3 supplement every day from birth to 12 months.
At around 6 months you need to start weaning your baby on to solid foods.
Measuring exact amounts of formula and water
It is important to measure the formula and water carefully. Too much or too little is not good for your baby.
For each 30mls (each ounce) of water, you need one level scoop of formula powder. Use the scoop in the formula box and run a clean knife across the top to level the scoop. For example, if you are making up a 90mls (3 ounces) feed, you will need to add 3 level scoops of formula to 90mls of cool boiled water.