Nutritionist Dr Federica Amati has challenged the popular 2-litre daily water rule, sharing what she says is the science-backed guidance on how much water you really need to drink each day13:09, 11 Jul 2026Updated 15:44, 11 Jul 2026The recent heatwave has left many Brits feeling dizzy, faint and exhausted. During these sweltering temperatures, staying hydrated is crucial.‌For years, the guidance to consume two litres of water daily has been widely regarded as essential for healthy living. The NHS advises drinking six to eight cups or glasses of fluid each day to maintain bodily health.‌"Water, lower-fat milk and sugar-free drinks, including tea and coffee, all count as part of your daily intake," the national health expert stated.‌However, one world-renowned nutrition expert has recently used social media to challenge the notion that everyone requires two litres of water daily.Nutritionist Dr Federica Amati posted on Instagram: "You may have heard you need two, three or maybe even four litres of water a day, but how much water do we actually need to drink?", reports the Express.'Cure' for grey hair close, first artificial cells created, humans and Neanderthals lived together, the world's fastest spider, and a ‘once-in-a-millennium’ chance to see an asteroid - all this and more in our weird science newsletter‌She added: "The truth is that for most young healthy people, hydration is not an issue. Hydration can become more of an issue with people who are sick and in the elderly because their thirst response is dampened which is a normal part of ageing."She explained that, as a general principle, listening to your thirst is the most effective way to remain hydrated. This means drinking whenever you feel thirsty, rather than striving to reach a target of two litres per day.‌Regarding rehydration salts, she advises against using them unless you've been through extreme circumstances, such as running a marathon or have been sweating heavily for several hours. She recommends that people avoid consuming them regularly as they can be high in sodium, which is a risk factor for hypertension and can be detrimental to your health.She went on to explain: "We have to remember that we get a lot of the water we need from our food, which is why eating whole fresh fruits and vegetables really contributes to your hydration levels."Can I drink too much water?A Nuffield Health expert stated: "Just like determining how much water is right for you, this all depends on the person and the environment they live in.‌"If we drink too much water, we risk losing valuable minerals like salt and potassium in our urine. If we drink too little, these minerals can start to crystallise and form kidney stones."Keeping yourself properly hydrated plays a vital role in maintaining your health, energy levels, and overall well-being. Your daily water requirements will differ depending on your age, body size, and how active you are, but a straightforward rule of thumb is to target around 35ml of water per kilogram of body weight, the expert noted.They pointed out that if you weigh 72kg (159lbs), aim for approximately 2.5 litres per day. If you weigh 85kg (188lbs), about three litres is needed, and if you weigh 100kg (220lbs), you need around 3.5 litres.Article continues belowBear in mind that you may require more if you lead an active lifestyle, exercise frequently, or spend time in hot conditions.