About half to two-thirds of your body is made up of water. That water is constantly on the move. Yet on a busy day, most people easily end up drinking too little without realising it. Read on to find out why it’s important to drink enough, roughly how much you need, and how to tell if you’re not drinking enough.
Why does your body need water?
Your body contains a lot of water and uses fluid throughout the day.
Water is found throughout your body, for example in your blood and in the synovial fluid in and around your joints. When you get warm, you sweat, and that sweat is largely water. Your urine consists largely of water.
Because your body uses fluid throughout the day, it helps to drink regularly.
How much water do you need each day?
For adults, a guideline of around 1.5 to 2 litres of fluid per day is often cited. Exactly how much you need depends on your body size, how much you exercise and the temperature.
This guideline refers to your total fluid intake, not just tap water. Your diet also counts: fruit and vegetables contain a lot of fluid, and fluids such as tea, coffee and soup contribute to the total. There’s no one-size-fits-all amount that’s right for everyone, but a few glasses spread throughout the day will usually do the trick.
Spreading your intake out is often better than drinking it all in one go. A glass of water when you get up, one with every meal, and a bottle within easy reach on your desk make it easier to stay hydrated without having to think about it too much.
When do you need more fluids?
Your fluid requirements aren’t the same every day. On hot days and during exercise, you lose more fluid through sweat, so you need more.
Your fluid needs go up in hot weather, during intense exercise, and when you’re losing extra fluid, for example with a fever or an upset stomach. It’s worth paying a bit more attention to your fluid intake at these times, rather than waiting until you feel very thirsty.
How can you tell if you’re not drinking enough?
Thirst is the best-known sign, but it’s a late one, so it helps to drink regularly rather than waiting until you feel very thirsty. The colour of your urine is a more useful daily guide.
Light yellow urine usually indicates that you’re drinking enough; darker urine is a sign that you should reach for your glass a bit more often. A dry mouth or a dry throat can also be a sign that it’s time to drink more. Want to know exactly what changes in your body when you don’t drink enough? Read more about what happens when you don’t drink enough water.
How much fluid do you lose when exercising?
During intense exercise, you can easily lose 1 to 2 litres of fluid per hour through sweat. So it’s a good idea to drink before, during and after exercise, rather than waiting until you feel thirsty.
Sweat consists of water and minerals, including sodium, potassium and magnesium. During prolonged or strenuous exercise, you lose not only fluid but also some of these minerals. You’ll normally replenish these minerals through a varied diet. You can read more about the role of magnesium in ‘What magnesium does for your body’. Tap water remains the basis of your daily fluid intake.
Frequently asked questions
How much water should you drink each day?
As a guideline, 1.5 to 2 litres of fluid per day is often recommended for adults. Your personal requirements depend on your body size, how much you exercise and the temperature; on hot days and during exercise, you’ll need more.
Does tea or coffee count towards your fluid intake?
Yes. Most drinks contribute to your total fluid intake, and water-rich foods such as vegetables, fruit and soup also count. The diuretic effect of a normal amount of coffee or tea is limited.
Can you drink too much water?
In exceptional cases, yes: drinking very large amounts in a short space of time can dilute the sodium levels in your blood. For most people, spreading your intake throughout the day and listening to your thirst is sufficient.
How do I know if I’m drinking enough?
The colour of your urine is a useful indicator: pale yellow usually indicates adequate hydration, whilst darker urine is a sign that you need to drink more often. Thirst is a late warning sign, so don’t wait for it.
