How to Prepare Baby Formula Safely
Always follow the instructions on your specific formula packaging first. Different brands and types of formula may have specific preparation requirements. The general steps below reflect WHO and NHS guidance but your formula label takes precedence.
If your baby is premature, under 2 months old, immunocompromised, or medically vulnerable [1], ask your paediatrician or neonatal team whether any additional precautions are needed for formula preparation and storage.
How you prepare formula matters. Incorrect preparation can affect both the safety and nutritional value of the feed. The steps below reflect guidance from the WHO, NHS, and most national health bodies.
Step-by-step preparation
- 1Wash your hands thoroughly with soap and water before preparing any feed.
- 2Clean and sterilise the bottle and teat. Use a steam steriliser, microwave steriliser, or cold water sterilising solution. Sterilisation of feeding equipment is recommended.
- 3Boil fresh tap water. Use water that has boiled once — do not use water that has been boiled multiple times, as repeated boiling concentrates minerals. Allow the water to cool for about five minutes, to no less than 70°C .
- 4Measure the correct volume of water into the sterilised bottle first, then add the formula powder. Always add water before powder — this ensures accurate concentration.
- 5Use the scoop provided in the formula tin. Level off each scoop with a clean, dry knife or the levelling device on the tin. Do not pack the powder or add extra scoops — this can cause the formula to be too concentrated and puts strain on your baby's kidneys.
- 6Put the cap on the bottle and shake well until the powder is completely dissolved.
- 7Cool the feed to body temperature by holding the bottle under cool running water or placing it in a bowl of cold water. Test the temperature by placing a few drops on the inside of your wrist — it should feel warm, not hot.
Why 70°C? Powdered formula is not sterile. Preparing it with water at 70°C or above kills Cronobacter sakazakii and other bacteria that can occasionally contaminate powdered formula [1]. Ready-to-feed (liquid) formula is sterile and does not require this step.
Water safety
In most developed countries, tap water is suitable for formula preparation once boiled. Bottled water is not recommended as the primary option — many bottled waters contain high levels of sodium, sulphate, or fluoride that are not appropriate for infants. If you use bottled water, choose still water labelled as suitable for infants.
If you are in an area with water quality concerns, follow local health authority guidance.
Storage of prepared formula
The safest approach is to make each feed fresh. If you need to prepare feeds in advance, prepared formula can be stored in the back of a refrigerator (not the door) for up to 24 hours [1]. Do not store prepared formula at room temperature.
When travelling, you can carry the correct volume of boiled water in a sealed, sterilised container and a pre-measured portion of formula powder separately, then combine them when needed.
Ready-to-feed formula
Ready-to-feed (RTF) liquid formula is sterile and does not need to be prepared with hot water. It is more expensive than powdered formula but useful for situations where safe preparation is difficult, such as travel or when access to boiling water is limited. Once opened, it should be used within the time stated on the pack and stored in the refrigerator.
Reheating formula
Do not use a microwave to reheat formula — microwaves heat unevenly and can create hot spots that can burn your baby's mouth. Use a bottle warmer or a bowl of warm water, and always test the temperature before feeding. Never reheat formula that has been partially consumed — discard leftover formula after each feed.
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