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Written by Alex Bussey
Edited by Mike Martin
Reviewed by the Your.MD Medical team
Your body needs water to flush out waste and toxins, hydrate your skin and carry nutrients to your cells.
Water also helps to regulate your body temperature (by letting you sweat), and plays an essential role in reducing the friction between your joints and keeping your eyes moist.
If you lose more water than you drink, you start to get dehydrated, and your body won’t have the fluids it needs to carry out these functions.
In the long term, not drinking enough water can also lead to constipation, kidney stones, urinary tract infections and kidney disease, so it’s important to know how much you need to drink, and how often you should be drinking.
It can be hard to work out exactly how much water you should be drinking to avoid dehydration. This can vary depending on your age, where you live, the temperature, the humidity, and the amount of exercise that you do.
Athletes, or people doing exercise that makes them sweat a lot, will need more water than someone who is less active. People who live in hot countries will also normally need more water than someone who lives in a cold climate.
Certain health conditions, including diabetes, can make you more prone to dehydration. Health issues such as food poisoning or heatstroke can leave you dehydrated.
Some medications can also have a diuretic effect, which means that taking them makes you need to pee more — increasing your chances of becoming dehydrated.
This makes coming up with a universal rule very difficult, but some organisations do offer useful guidelines.
The UK’s National Health Service recommends that everyone try to drink at least 6 to 8 glasses of water per day.
The American Heart Association recommends checking the colour of your pee to make sure that you're drinking enough water. The darker it is, the more dehydrated you are.
The Association of British Dietitians (BDA) has more detailed guidelines, based on your age and gender.
|Group||Adequate water intake from drinks (ml/day)|
|Adults (anyone over 14 years old)||Men: 2000ml, Women: 1600ml|
|Pregnant women||As adults + 300ml per day|
|Lactating women||As adults + 600-700ml per day|
The BDA also outlines the best sources of water, as many foods are also hydrating. It says that 70 to 80% of the water that you need should come from the fluids that you drink.
The remaining 20 to 30% of water should come from foods like soups, stews or water-rich vegetables like celery and cucumber, and fruits like tomatoes or melon.
To make sure you stay hydrated following a workout, you can weigh yourself before and after exercise, to see how much water you’ve lost by sweating.
You need to drink approximately 500ml of water for every 450g of sweat that you lose.
One of the first signs of dehydration is thirst, but feelings of thirst aren’t always a reliable indicator of dehydration. Some people mistake thirst for hunger, and some experts say that by the time you feel thirsty, you may already be dehydrated.
So what signs should you look out for?
The colour of your pee can be a good indicator. It should normally be a pale yellow, while dark urine is normally a sign that you are dehydrated.
Other signs of dehydration include:
If you become severely dehydrated, you may stop passing urine completely. You may also feel lightheaded when you try to stand up or move around, and you may notice that your skin becomes less elastic (stretchy).
Other symptoms of severe dehydration include low blood pressure, a rapid heart, fever, lethargy and confusion.
Severe dehydration is a medical emergency. If you notice signs or symptoms you should seek medical attention immediately.
If left untreated, severe dehydration can damage organs like your liver, kidneys and your brain.
Mild to moderate dehydration can often be treated at home.
You should drink plenty of fluids, and try to eat a salty snack like a packet of crisps to replace any lost nutrients. You can also take an oral rehydration solution to replenish lost salts.
Chronic or severe dehydration can be a medical emergency. You should go straight to the nearest emergency room if you're feeling unusually tired, confused or disoriented.
Drinking more water than your body needs can lead to a condition called hyponatremia. This is where excess water dilutes the sodium in your blood, and causes your cells to swell up — putting pressure on important organs like your brain.
But overhydration is rare, because your kidneys can normally get rid of extra water before it becomes a problem.
Overhydration mainly affects people like athletes, who drink large amounts of water to try and avoid dehydration. It also affects people whose kidneys don't pass water properly, including people with long-term health conditions like kidney failure and congestive heart failure.
Some antidepressants are also thought to increase the risk of overhydration.
Symptoms of mild overhydration include tiredness and difficulty concentrating, but the condition does cause more serious symptoms as it progresses. These include vomiting or nausea, problems with balance, muscle weakness, muscle twitches, confusion and seizures.
Overhydration should be diagnosed and treated by a specialist. If you think that you might be overhydrated, see a doctor as soon as you can.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.