Why You Should Never, Ever Add Too Much Water To Your Baby's Formula

Mixing formula with water, but babies aren't allowed water? How does that work?
RuslanDashinsky via Getty Images

Until you’re a parent, you don’t really think about the fact that babies aren’t actually allowed to have water until they’re six months old.

Upon sharing this fact with many of my friends who do not have kids, they’re always baffled by it. 90% of them have no clue that this was even a thing — and to be honest, neither did I until I became a mum.

But one TikTok is going viral after debunking the idea that babies aren’t allowed water, yet we mix their formula with water. So how does that work?

Dr Karan Rajan, an NHS surgeon and TikToker who often does explainers on medical issues on both TikTok and Instagram revealed why this is the case.

He advised not to give babies extra water to drink until they are at least six months old as it could be fatal.

He said: “Newborn babies have kidneys that are half the size, or less than that of an adults. Their kidneys are still undergoing software updates so they’re not mature enough to correctly filter large volumes of plain water.

“Human breast milk is 87% water, formula milk is around 85% water. But importantly, both of these contain nutrients and electrolytes mixed in with carefully controlled amounts of water which is safe for the baby.

“Giving too much additional water either by over dilution of the formula or giving it separately causes the extra water to dilute the salt in the blood, causing hyponatraemia — very low sodium.”

He went on to explain that this can be very dangerous as it can lead to brain swelling, seizures, water intoxication and even death.

He added: “Adults can get water intoxication too but only if they drink several litres of water in a short space of time, for a baby the margins are a lot smaller. But don’t worry, these little creatures can meet their hydration needs with breast milk or appropriately mixed formula.

“Also before the age of six months their stomach capacity is tiny. They also have a slower gastric emptying, meaning they fill up very quickly.

“Giving additional water means they become too full so they don’t have the appetite to drink milk, this can lead to energy and nutrient deficiency,

TikTokers were quick to comment on the video, which has garnered a quarter of a million views, one person said: “Babies literally need to come with a manual when discharged from hospital cuz I did not know this. Those kidneys would’ve been hydrated.”