How much water should I drink?

From flushing out toxins to digestion, we require water for almost every bodily function. Feeling thirsty and passing dark coloured, strong-smelling urine are some of the initial signs that you could be dehydrated

(Rex)

Why drinking water is important

More than two thirds of the human body consists of water. We require water for almost every function within our bodies, from flushing out toxins to digestion.

But knowing how much water to drink can be a challenge, particularly when it’s warm or you’re doing more exercise than usual.

Drink too little and it’s possible to suffer some potentially serious health problems. However, to complicate matters, drinking too much also carries health risks.

How much water should you drink per day?

Under normal circumstances, the amount of water in the body is controlled by the thirst response and urine production: you’re thirsty, you drink, you go to the toilet – the water cycle starts again.

In 2010, a report from The European Food Safety Authority suggested that the minimum levels of water consumption should be 2 litres for men and 1.6 litres for women, or between eight and ten glasses. For men, their daily requirement of two litres of water is equivalent to just over three and a half pints. For women, their recommended intake of 1.6 litres of water is the equivalent of just under three pints. A standard soft drink can in the UK contains 330ml of fluid, and the average bottle of water is 500ml (a man would need to drink the equivalent of four bottles of water, and a woman would need to drink the equivalent of just over three bottles of water).

However, much depends upon the level of activity that you engage in, your physical health, your size and weight and whether it’s a hot day or not.

I would always recommend that drinking water little and often is the best way to stay hydrated.

What you drink is important too. While alcohol may quench your thirst, it’s actually a diuretic. This means it may make you need to pass urine more often, potentially leading to dehydration. When people experience a hangover, one of the key components of this is dehydration. The typical hangover headache is a symptom of this. A good tip is to alternate every alcoholic drink with a glass of water.

Drinking milk, water and fruit juices are all good ways of maintaining hydration. However, always bear in mind the amount of sugar that might be contained within any sweetened drink. Tea and coffee may also help but try to keep track of how much caffeine you are consuming.

How do you know if you are dehydrated?

Feeling thirsty and passing dark coloured, strong-smelling urine are some of the initial signs that you could be dehydrated. Other symptoms can include feeling sluggish, feeling light headed and or having a dry mouth.

People at the extremes of age, such as children and the elderly, are more at risk of becoming dehydrated. Signs that might give your doctor cause for concern is if children are becoming drowsy, having fewer wet nappies or if they are breathing more quickly. Older people often may not realise that they are dehydrated and confusion is a common presentation of dehydration in the elderly.

Patients experiencing vomiting, diarrhoea or sweats as a result of a fever can become dehydrated quickly unless they are able to replace the extra water lost from the body.

Is it possible to be overhydrated?

It is possible to drink too much, although a person with healthy kidneys is normally able to deal with that by visiting the toilet more often.

Overhydration occurs when the body retains or collects too much water. This can lead to water intoxication and sodium levels that are dangerously low, which is referred to as hyponatraemia.

Some athletes who participate in endurance events, especially marathon runners, can be prone to taking on too much fluid and suffering from hyponatraemia. A study in the Clinical Journal of Sports Medicine this month has looked at replacement of fluids in athletes, with the concluding advice that those participating in sports should drink according to their thirst levels.

In some cases, there are medical reasons why the body is unable to cope with excess water. This water retention tends to affect people with kidney and heart conditions. Swollen ankles is a common sign of water retention.

In order to help the body to relieve itself of excess water, and to relieve pressure on the heart and other organs, doctors use diuretics or water tablets that promote the production of urine.

Time to see the doctor?

There are certain circumstances in which people should seek urgent medical attention. They include not passing urine for more than eight hours, feeling lightheaded or lethargic, confusion or a pulse that feels rapid.

Constantly feeling thirsty can also be a symptom of other chronic conditions, including diabetes.

For most healthy people, drinking little and often throughout the day is the best approach. Drink a little more, but not too much, when it’s hot or you are exercising.

Listen to your body and it will let you know whether you are drinking too much or too little. But don’t be afraid to seek medical advice if anything seems out of the ordinary.

Dr Alexandra Phelan is an NHS GP and member of the Pharmacy2u.co.uk Online Doctor Service team.