Your body needs water or other fluids to work properly and to avoid dehydration.
This article explains how much we need to drink, how to spot the signs of dehydration and how to choose healthier non-alcoholic drinks. For advice on alcohol, see our Alcohol section.
Water makes up about two-thirds of the weight of a healthy body.
Most of the chemical reactions that happen in our cells need water in order to take place. We also need water so that our blood can carry nutrients around the body and get rid of waste.
How much should we drink?
To stay healthy, it's important to replace the fluid we lose when we breathe, sweat or urinate.
We get some fluid from our food but most comes from drinks.
The European Food Safety Authority recommends that women should drink about 1.6 litres of fluid and men should drink about 2.0 litres of fluid per day. That's about eight 200ml glasses for a woman and 10 200ml glasses for a man.
However, the amount a person needs to drink to avoid getting dehydrated will vary depending on a range of factors, including their size, the temperature and how active they are. So, for example, if you're exercising hard in hot weather you'll need to drink more.
All drinks count, including hot drinks such as tea and coffee, but water, milk and fruit juices are the healthiest. It is best to avoid alcoholic drinks.
Try to avoid sugary, soft and fizzy drinks that can be high in added sugars. These can be high in calories and bad for teeth.