Can you use distilled water for formula?

The verdict

Distilled water is water with the minerals taken out. That is all it is. It does not make formula safer, and in the UK and Ireland it does not remove a single step from the method.

The reason parents ask is a misunderstanding about where the risk sits. The concern in powdered formula is not the water. It is the powder. Powdered infant formula is not a sterile product and can contain harmful bacteria, which is why UK and Irish guidance builds every feed around water hot enough to kill them.

The 70C rule, and what it is for

The NHS instruction is precise: boil fresh tap water, leave it to cool for no more than 30 minutes so it remains at a temperature of at least 70C, and put the water into the bottle first, while it is still hot, before adding the powder. Water at 70C or more will kill any harmful bacteria.

The organism this is aimed at is Cronobacter sakazakii, along with Salmonella. Cronobacter infection in newborns is rare and serious, and it has been linked to powdered formula. The 70C step is the control measure, and it works only if the water is genuinely still that hot when it hits the powder, which is why the 30-minute window exists rather than a vague instruction to let it cool.

Distilled water boiled and used at 70C would satisfy that rule. Distilled water poured cold from a bottle onto powder would not, whatever the label says about purity.

Why fresh water, and not re-boiled

Both the NHS and the HSE specify fresh tap water rather than water that has been boiled before, and the NHS also rules out artificially softened water. Repeated boiling concentrates whatever minerals are present, and softened water is higher in sodium than a baby should have.

What distilled, purified and nursery water actually are

Distilled water is produced by boiling water and condensing the steam, leaving minerals behind. Purified water is a broader category, usually produced by reverse osmosis or deionisation. Water sold as nursery water is bottled drinking water marketed for infant feeding, sometimes with fluoride added and sometimes not.

None of these is sterile in the sense that matters. Distillation kills organisms during the process, but the product is then bottled, sealed and stored, and once opened it is an ordinary open container. UK and Irish guidance treats all bottled water the same way: if you use it, boil it.

There is one genuine trade-off in the US context, and it is dental rather than microbiological. Distilled and purified waters contain no fluoride. AAP guidance is to primarily use safe fluoridated tap water and occasionally some non-fluoridated bottled water, because exclusively using fluoride-free water removes a source of protection against tooth decay.

Where guidance differs

This is one of the sharpest and least-discussed disagreements in infant feeding, and both positions are named here because parents routinely find one and assume the other is wrong.

The NHS and the HSE require freshly boiled water at 70C or above for every powdered feed, for every baby, regardless of age or health. Cooling for no more than 30 minutes is how you get there. Feeds are made one at a time wherever possible.

The AAP requires boiled water for a defined group only: infants younger than 2 months, those born prematurely, and those with a weakened immune system. For everyone else, its guidance allows powdered formula to be mixed with room temperature tap water immediately before feeding, and it notes such a bottle needs no refrigeration or warming.

Both are considered positions. The UK approach treats every feed as a potential exposure and removes the risk at source. The US approach targets the babies in whom Cronobacter infection is most likely to be catastrophic, and accepts the residual risk elsewhere in exchange for a method families can actually follow at 3am.

If you are in the UK or Ireland, follow the 70C method. If you are in the US, follow the AAP rule and boil for the named groups. Do not mix a US preparation method with a UK claim that it is equivalent, because it is not.

Preparation machines and the same trap

Formula preparation machines dispense water at a set temperature. The NHS is explicit that if you use one, you must make sure the water that comes out is at least 70C when it is mixed with the powder, and suggests checking with a digital food thermometer. If it is below 70C, stop using the machine and follow the step-by-step method instead.

The HSE makes the same warning about bottle warmer machines, noting the risk that they do not heat water to the 70 degrees Celsius required to make a bottle safely.

If you have been using cold bottled or distilled water

Do not treat past feeds as an emergency. The absolute risk of Cronobacter infection is low, which is why this is guidance rather than an alert.

Change the method from the next feed: fresh tap water, boiled, cooled no more than 30 minutes, water in first, then powder, then cool the made-up bottle under a running cold tap and test on your wrist.

If your baby is under two months, was born preterm, or has a weakened immune system, this matters more, and every authority agrees on that group. If your baby is unwell, particularly with fever, poor feeding, unusual sleepiness, irritability or a bulging fontanelle, seek medical help urgently and say how feeds have been made up.