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How much water should we drink?

Water is essential for good health but over drinking can be fatal. What are the signs of dehydration and how much water should we drink?   2015-08-13

Water makes up between 50 and 70% of an adult's total body weight; therefore we need regular top-ups to replace the water we lose through our breath, sweat, urine and bowel movement. Water is required for all our body systems, it flushes out toxins, helps blood carry nutrients round the body and provides moisture for ear, nose and throat tissues. We are not able to survive if we don’t keep our fluid levels in balance. Not many of us will ever have to make the choice between going without food and having no water. However, we know that a person can survive for up to 3 months without food whereas you are unlikely to last more than 3 or 4 days without water.

Drink too little and risk dehydration but drinking too much can be harmful. So how much water do we need?

This depends on whether it’s a hot day, on how active you are, your age, size and weight but a good guide is to trust your thirst response. If you are thirsty, your mouth is dry or you aren’t urinating enough, it’s a sign that you have to drink.

Signs of dehydration

  • Headache
  • Tiredness
  • Loss of concentration
  • Dry mouth, lips and eyes,
  • Your urine is a dark colour, when it should be straw coloured. However, your body is good at regulating this system and most people find that if they are dehydrated they don’t want to pee whereas if they have had too much to drink they will be making lots of trips to the loo.

Myths and facts

  • Tea and Coffee will make you dehydrated?

The answer is both yes and no. Caffeine can be dehydrating if consumed in large amounts, however if your tea and coffee intake is moderate, the water contained in the drink will more than compensate for the effect of the caffeine and will have the same rehydrating effect as any other liquid. Alcohol is always dehydrating and many people will be familiar with the extreme thirst that is typical of the ‘morning after the night before’.

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  • Detox diets are important for our health?

The idea that we need to ‘detox’ our bodies has become established as a fact in the minds of many people. However, the overwhelming majority of medical scientists disagree with this assertion, pointing out that the kidneys and liver do a perfectly good job of removing toxins and reminding us that a year round balanced diet and drinking water are far more beneficial to health than extreme diets or fasts.

  • Soft drinks

Water has been and will always be the healthiest and best way of satiating our thirst. Soft drinks are high in sugar and have been linked to metabolic syndrome, diabetes and heart disease. Diet drinks are no better and they may be linked to long term weight gain and ill health. So our advice is set aside those soft drinks for socialising and train yourself to drink water if you are thirsty.


We all know that dehydration can be fatal but is there such a thing as overhydration? Normally the kidneys get rid of excess water but overhydration happens when we drink more water than the kidneys can get rid of. Sometimes called Exercise-associated Hyponatraemia (EAH) or Water Intoxication too much water in the body results in a low blood sodium concentration and can cause the brain to swell, causing confusion, loss of consciousness and seizures. The death of sportsmen from EAH is not unknown.


Exercise-associated Hyponatraemia is usually associated with endurance athletes who are scared into over drinking. Worries of EAH should not coerce us into the risk of dehydration. Listen to your body, if you are thirsty, have a dry mouthy or aren’t urinating sufficiently, quench your thirst with an ice cold glass of water, it’s one of the pleasures of life.