How much water do you need?

How much water you need depends on body size, activity, climate and health. The European Food Safety Authority (EFSA) considers about 2 litres a day of total water adequate for women and about 2.5 litres for men, from drinks and food together; part of it comes from food. Needs rise in hot, humid weather and with physical work.

Simple signs

• Thirst is the body’s normal signal to drink.
• Pale yellow urine usually suggests enough fluid.
• Dark urine, headache or tiredness can be signs of not drinking enough. Some vitamins and medicines change urine colour.

Habits that help

• Keep a bottle of safe drinking water within reach.
• Drink at regular intervals in hot weather and when working outdoors.
• Water is the best everyday drink; sweet drinks add sugar.
• Drink safe water: boiled or properly filtered.

When to be careful

People with heart failure, kidney disease or liver disease are sometimes told to limit fluids; if so, follow your doctor’s advice. With diarrhoea, oral rehydration solution (ORS, orsaline) helps replace water and salts. Seek medical care quickly if symptoms are severe or last, especially for children and older adults.

This article is general information, not personal advice. If you have a medical condition, are pregnant, or take regular medicine, ask your doctor or a dietitian before making major changes to your diet.

Sources

• EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for water. EFSA Journal 2010;8(3):1459.
• World Health Organization. Diarrhoeal disease. Fact sheet.