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Preparing baby formula

Powdered infant formula is not sterile. This means that there may be bacteria in the infant formula powder and 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.


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 also get plug-in or microwaveable sterilisers.

How to prepare baby formula

  1. Boil 1 litre of cold tap water in a kettle.
  2. Leave the boiled water to cool in the kettle for 30 minutes - but no longer. This will make sure that the water is at least 70 degrees Celsius.
  3. Clean the work surface well. Wash your hands with soap and warm water. Dry them on a clean towel.
  4. Read the instructions on the formula’s label carefully to find out how much water and powder you need.
  5. Pour the correct amount of water into a sterilised bottle. Water that is 70 degrees Celsius is still hot enough to scald, so be careful.
  6. Add the exact amount of formula to the boiled water, using the clean scoop provided. Adding too much or too little formula could make your baby sick. Reseal the packaging to protect it from germs and moisture.
  7. Screw the bottle lid tightly and shake well to mix the contents.
  8. 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.
  9. To check the feed is not too hot, shake the bottle and place a drop of liquid on the inside of your wrist. It should feel lukewarm, not hot.
  10. Feed your baby.
  11. Throw away any feed that your baby has not taken within 2 hours. If your baby is a slow feeder use a fresh feed after 2 hours.
  12. After a feed, clean and rinse the bottle and teat.

How to give a baby a bottle

Types of formula milk

Using bottled water

You may need to use bottled water to make up feeds if you:

  • have a water softener system (tap water from a water softener system may contain too much sodium)
  • have been told to boil all tap water before use
  • are on holiday abroad

When using bottled water, always:

  • boil the bottled water before using it to make up feeds
  • use still water only - never fizzy or sparkling water
  • avoid using bottled water labelled as ‘natural mineral water’ – this can have higher levels of sodium and other minerals

How much formula your baby needs

This table is a guide only. Talk to your public health nurse (PHN) 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 2 hours.

At around 6 months you can start weaning your baby on to solid foods.

Your baby's age Number of feeds per day Amount of formula feed to use each day (per baby weight)
Your baby's age Birth to 3 months Number of feeds per day 6 to 8 (every 3 to 4 hours) Amount of formula feed to use each day (per baby weight) 150ml per kilogram (kg)
Your baby's age 4 to 6 months Number of feeds per day 4 to 6 (every 4 to 6 hours) Amount of formula feed to use each day (per baby weight) 150ml per kilogram (kg)

To find out how much formula your baby needs per day, multiply 150ml by their weight in kilograms (kg).

Vitamin D3 supplement for babies

You should give your baby 5 micrograms of vitamin D3 as a supplement every day from birth to 12 months if they are:

  • breastfed
  • taking less than 300ml of infant formula a day

You do not need to give your baby a vitamin D3 supplement if they are fed more than 300ml of infant formula a day. Infant formula now comes with vitamin D added to it.

Vitamin D for babies 0 to 12 months

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 30ml of water, you need 1 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 90ml feed, you will need to add 3 level scoops of formula to 90ml of cool boiled water.

Formula preparation machines

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.

Using expressed breast milk or infant formula safely - fsai.ie

Feeding options

Your midwife or public health nurse can give you advice on formula feeding and other feeding options. They can help if you want to breastfeed but are having difficulties.

You can also talk about breastfeeding to a:

There may be a number of options available to you.

You can

If you want to restart breastfeeding, you can get support.

Page last reviewed: 10 November 2022
Next review due: 10 November 2025