Making up infant formula

Your baby’s immune system is not as strong or well developed as an adult’s, so babies are much more prone to illness and infection. This means that good hygiene is very important when making up a feed.

All equipment used to feed your baby must be sterilised. Bottles, teats and any other feeding equipment need to be cleaned and sterilised before each feed to reduce the chances of your baby falling sick or getting diarrhoea.

Bacteria in infant formula

Even when tins and packets of powdered infant formula are sealed, they can sometimes contain bacteria such as Cronobacter sakazakii and, more rarely, salmonella. Although these bacteria are very rare, the infections they cause can be life-threatening.

Bacteria multiply very fast at room temperature. Even when the feed is kept in a fridge, bacteria can still survive and multiply, although they do this more slowly.

To reduce the risk of infection, it's best to make up feeds one at a time, as your baby needs them.

Use freshly boiled drinking water from the tap to make up a feed. Don't use artificially softened water or water that has been boiled before.

Leave the water to cool in the kettle for no more than 30 minutes. This will ensure it stays at a temperature of at least 70C. Water at this temperature will kill any harmful bacteria. Remember to let the feed cool a little more before you give it to your baby.

Don't use bottled water when making up formula milk

Bottled water is not recommended for making up feeds, as it's not sterile and may contain too much salt (sodium) or sulphate. If you have to use bottled water to make up a feed, check the label to make sure the sodium (also written as Na) level is less than 200 milligrams (mg) per litre, and the sulphate (also written as SO or SO4) content is not higher than 250mg per litre. It's not usually sterile so, like tap water, it will still need to be boiled before you prepare the feed.

Step-by-step guide to preparing a formula feed

• Step 1 Fill the kettle with at least 1 litre of fresh tap water (don’t use water that has been boiled before).
• Step 2 Boil the water. Then leave the water to cool for no more than 30 minutes, so that it remains at a temperature of at least 70C.
• Step 3 Clean and disinfect the surface you are going to use.
• Step 4 It’s very important that you wash your hands.
• Step 5 If you are using a cold-water steriliser, shake off any excess solution from the bottle and the teat, or rinse the bottle with cooled boiled water from the kettle (not tap water).
• Step 6 Stand the bottle on a clean surface.
• Step 7 Keep the teat and cap on the upturned lid of the steriliser. Avoid putting them on the work surface.
• Step 8 Follow the manufacturer’s instructions and pour the amount of water you need into the bottle. Double check that the water level is correct. Always put the water in the bottle first, while it is still hot, before adding the powdered infant formula.
• Step 9 Loosely fill the scoop with formula, according to the manufacturer’s instructions, and level it off using either the flat edge of a clean, dry knife or the leveller provided. Different tins of formula come with different scoops. Make sure you only use the scoop that is enclosed with the powdered infant formula you are using.
• Step 10 Holding the edge of the teat, put it on the bottle. Then screw the retaining ring onto the bottle.
• Step 11 Cover the teat with the cap and shake the bottle until the powder is dissolved.
• Step 12 It's important to cool the formula so it's not too hot to drink. Do this by holding the bottom half of the bottle under cold running water. Make sure the water does not touch the cap covering the teat.
• Step 13 Test the temperature of the formula on the inside of your wrist before giving it to your baby. It should be body temperature, which means it should feel warm or cool, but not hot.
• Step 14 If there is any made-up formula left after a feed, throw it away.

Dos and don'ts of making up infant formula

• As manufacturers’ instructions vary as to how much water and powder to use, it's important to follow the instructions very carefully.
• Do not add extra formula powder when making up a feed. This can make your baby constipated and may cause dehydration. Too little powdered infant formula may not provide your baby with enough nourishment.
• Do not add sugar or cereals to the feed in the bottle.
• Never warm up infant formula in a microwave, as it can heat the feed unevenly and may burn your baby’s mouth.

More information

Read more about Combining breast and bottle feeding