From Hot Girl Walks to treadmill workouts, TikTok has been responsible for many of the health and fitness trends we jump on. But taking the crown for the most popular trend is the ‘30 day gallon challenge’, with a third of British social media users trying it, according to sports bra brand Hunkemöller.

As it says on the tin, the ‘challenge’ is to drink a gallon (4.5 litres) of water every day for 30 days. People claim that it makes their skin glow, their energy levels rise and rids them of their bloating. 

And given 33% of us are planning on kickstarting our September wellbeing routine by drinking more water, according to Holland & Barrett, you might be tempted to jump on this trend. But it’s a huge amount of water to drink every day – over twice as much as the roughly recommended two-litre intake advised by the NHS. 

Should you drink a gallon of water a day? 

As with all well-being advice, it depends on the individual. Dr Noel Young, clinical innovation associate at Thriva, explains that “how much water you need depends on several factors. Things like your environment, how active you are, your age and whether you have any medical conditions.”

In hot weather, drinking more is probably necessary – but within reason. While “there’s no universal limit on how much water you should drink every day,” according to Dr Young, “it’s important to get the balance right, because drinking too much water, especially in a short amount of time, can be dangerous.”

Why is drinking too much water a problem?

Dr Young points to a 2013 paper from the American College of Sports Medicine’s Health & Fitness Journal that reported “hyperhydration (i.e., “water intoxication”) can present with symptoms such as fatigue, lethargy, disorientation, confusion, headache, nausea and vomiting”.

It’s because water can flush out sodium, and “excess hydration can cause an imbalance in blood salts and impact the brain,” he says.

That’s particularly true if you are exercising a lot. While keeping hydrated during hot weather workouts is essential, you need to be sure to take on electrolytes with your water to avoid an imbalance of salts you lose in sweat.

Explaining the concept, Jo Jacobius from The Water Dispenser and Hydration Association tells Stylist: “Excessive quantities of liquid can lead to hyponatraemic encephalopathy – a condition in which the blood becomes so diluted that the salt level falls and fluid is drawn into the brain under osmotic pressure, causing it to swell.”

It’s a rare condition, but the point is that drinking too much can be an issue. It’s why relying on ‘trends’ can be so dangerous. “Trends like this don’t factor in the fact that our fluid requirements change day to day. It’s important to follow your body’s cues, not the pressure of what you see online,” says Dr Young. 

That means you shouldn’t rigidly stick to the two-litre rule or the gallon challenge. “The guidance about drinking 1.8 to two litres a day is based on the need to replenish the quantity of fluids most adults lose on an average day in average temperatures… but the average is only a guideline.”

How to stay hydrated 

Staying hydrated is important, but you don’t need excess amounts to reap the skin, gut and energising benefits.

There are more efficient ways to monitor your hydration levels than forcing yourself to drink. “Pay attention to your body’s cues, including your thirst levels. You can count hydration levels in food, tea and coffee and make sure to carry a water bottle with you when you go out,” says Dr Young.

Staying hydrated in the heatwave is unarguably important, but you can have too much of a good thing. 

Images: Getty