Infant formula should be prepared with water from a safe source and with the exact water-to-powder ratio printed on the product label. The right preparation method depends on both the safety of the water and the baby's risk factors. Powdered infant formula itself is not sterile, so water safety and formula-preparation safety are related but separate issues.
This guide is educational. If your baby is younger than 2 months, was born prematurely, has a weakened immune system, or has another medical feeding need, ask your pediatrician whether extra preparation precautions or a sterile ready-to-feed formula are appropriate.
Can you use tap water for baby formula?
FDA guidance says to use water from a safe source. If you are confident that your public tap water is safe to drink, it can generally be used according to the formula label. If you are unsure about your tap water or use a private well, contact your local health department or water authority rather than relying on appearance, taste, or smell.
If local authorities issue a boil-water notice or say the water is unsafe, follow that emergency guidance. FDA advises using bottled water during a water-supply emergency when tap water is polluted or unavailable.
Is bottled water safer than tap water?
Not automatically. The FDA states that ordinary bottled water is not sterile unless the label specifically says it is sterile. Ordinary bottled water used for formula should therefore not be treated as germ-free simply because the bottle is sealed.
Water marketed as sterile for infants must meet specific FDA sterility requirements. If you use ordinary bottled water, follow the same formula-preparation precautions you would use with other safe drinking water and follow the current product label.
Powdered formula is not sterile
Safe drinking water does not make powdered formula sterile. CDC notes that powdered infant formula can occasionally contain germs such as Cronobacter. Babies younger than 2 months, babies born prematurely, and babies with weakened immune systems are at higher risk from these infections.
For higher-risk babies, CDC describes additional preparation steps when powdered formula must be used: boil water, allow it to cool for no longer than about five minutes, mix the powder while the water is still very hot (at least 158°F / 70°C), then cool the prepared bottle to a safe feeding temperature. Ask your baby's health-care professional whether these extra precautions apply to your situation.
FDA and CDC also note that sterile liquid ready-to-feed formula can be a safer option for higher-risk infants because it does not require mixing with water.
A safe preparation sequence
- Wash your hands and use clean feeding equipment and a clean preparation surface.
- Use water from a confirmed safe source.
- Measure the exact amount of water first.
- Add the exact amount of powder stated on the label using the scoop supplied with that formula.
- Mix according to the manufacturer's instructions. Never add extra water or extra powder.
- If extra hot-water precautions are being used for a higher-risk baby, cool the prepared formula to a safe feeding temperature before feeding.
- Follow the time and storage limits below.
Do not substitute another product's scoop or mixing ratio. Different formulas can use different scoop sizes and dilution instructions.
What about filtered water?
A household filter only removes the contaminants it is certified to remove. A filter that improves taste or reduces chlorine should not be assumed to remove bacteria, lead, nitrates, or every other contaminant. Check the filter certification and your local water report. If the underlying water source is not known to be safe, contact the local water authority or health department.
What about private well water?
Private wells are not monitored in the same way as public water systems. Before using well water for an infant, have the water assessed according to local public-health recommendations. If you do not know whether the water is safe, do not guess based on taste or clarity.
Water emergencies
Flooding, broken water mains and other emergencies can make a normally safe source temporarily unsafe. Follow local public-health instructions. FDA advises using bottled water to prepare formula when the tap supply is polluted or cut off. If potentially contaminated tap water must be used, follow the current disinfection instructions from the relevant authority before preparing a feed.
Formula storage after preparation
- Within 2 hours of preparation: use prepared formula if it has remained at room temperature and feeding has not started.
- Within 1 hour from the start of feeding: discard any formula left in a bottle the baby has drunk from.
- Within 24 hours: if a freshly prepared bottle will not be used within 2 hours, refrigerate it immediately and use it within 24 hours.
- Do not freeze prepared formula.
For related safety information, see Baby Formula Preparation Guides, Can You Refrigerate or Freeze Baby Formula?, and How to Warm Formula From the Fridge Safely.
Official sources
- FDA — Handling Infant Formula Safely: What You Need to Know
- FDA — Infant Formula: Safety Do's and Don'ts
- CDC — Cronobacter Prevention
- CDC — Infant Formula Preparation and Storage
Formula labels and public-health guidance can change. Use the current instructions for the exact formula and current local water guidance.