It shouldn’t be that hard to drink eight glasses of fluids over the course of an entire day – that’s not even one glass an hour. Yet very few of us actually manage to do it.

Mind you, perhaps it’s not quite as easy as it sounds. While NHS guidelines recommend we should drink 1.2 litres (around six to eight glasses) of fluid every day, they also accept that “it can vary”.

So how can you make sure you’re sufficiently hydrated? Here are our top tips.

Drink at least two litres

“There is currently no agreement on the amount of fluid you need on a daily basis,” confirms GP, Dr Sarah Brewer.

But the six to eight glasses estimate is about right. “The amount of water an adult loses, during an averagely active day, is around 2.5 to 3 litres,” Dr Brewer continues.

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“This is mainly lost through the lungs as water vapour, through the skin as sweat, and through the kidneys as urine. To replace this amount, you ideally need to drink at least two litres (eight glasses) of water per day, in addition to other fluids such as alcohol, tea, coffee and soft drinks.”

Drink more when you exercise

“When taking vigorous exercise, or visiting a hot country, however, you may need to drink twice this amount or more. Athletes in hot climates may lose as much as 10 litres of fluid per day!”

Dr Brewer adds the simple tip that “for every 20 minutes of exercise you take during the day, your fluid intake should increase by a further 250ml.”

Drink before you’re thirsty

Grabbing some liquid when you’re already gasping could be a case of too little too late.

“Although the body has mechanisms to help control fluid loss through the kidneys, by the time you feel thirsty, you are already significantly dehydrated,” points out Dr Brewer.

Check your urine

“An early warning sign of dehydration is passing less urine than normal, which is darker in colour,” she adds. “Aim to drink sufficient fluid to maintain a normal volume of urine, which is also pale coloured.”

Know the basic symptoms

Dehydration affects the way your cells work, upsetting the body’s balance of minerals (salts and sugar) in your body, and “leading to lack of energy, tiredness, poor concentration, reduced alertness, recurrent headaches and mood changes.”

Other symptoms may include:
• dizziness or light-headedness
• dry mouth, lips and eyes
• passing small amounts of urine infrequently (less than three or four times a day)

Know the extreme symptoms

If dehydration is not addressed in response to early symptoms, it can become a medical emergency. Seek treatment and advice if you notice any of the following symptoms:
• feeling tired or confused
• dry mouth and eyes that do not produce tears
• not passing urine for eight hours
• dry skin that sags slowly into position when pinched up
• rapid heartbeat
• blood in your stools or vomit
• low blood pressure
• irritability
• sunken eyes
• a weak pulse
• cool hands and feet
• fits (seizures)
• a low level of consciousness

Know your fluid sources

“Drink fluids regularly throughout the day, rather than just drinking when you feel thirsty. Carry a bottle of water or sports drinks and sip regularly,” advises Dr Brewer.

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But it’s not all about the water: “Some foods are good sources of fluid, such as low-fat milk as used on a bowl of cereal, soups, melons, cucumbers and other juicy fruit and vegetables.

“Herbal (non-caffeinated) teas are both refreshing and an excellent source of fluid that counts towards your total water intake,” adds Dr Brewer. “Iced mint, lemon and other herbal teas also make a great summer drink.”

Know the benefits

Apart from staving off the potentially dangerous effects of dehydration, keeping your fluid levels has some added bonuses too.

“Dehydration can affect exercise performance even when you’re only moderately short of fluids (less than 2% dehydrated), and this level of dehydration can occur during exercise itself, as a result of sweating, even if you were sufficiently hydrated before.

“Good hydration is also important for healthy, glowing skin with good elasticity (known as turgor). Dehydration promotes dryness and wrinkling, which has an ageing effect on your looks.”

How much water do you drink a day? Tell us in the Comments box below.