Nutrition1 min read
How much water should you drink a day?
The truth about the eight-glasses rule, how food counts towards your fluids, and simple signs you're drinking enough.
"Drink eight glasses of water a day" is one of the most repeated pieces of health advice there is. It's a reasonable reminder, but it isn't based on a precise scientific rule. How much you need depends on your body, your activity and your environment.
What the guidelines say
The US National Academies set an adequate total water intake of about 2.7 litres a day for women and 3.7 litres for men. That's total water, from all drinks and food combined, not just plain water. Food typically provides around a fifth of it.
Food and other drinks count
- Fruit and vegetables like cucumber, watermelon, oranges and lettuce are mostly water
- Soups, stews, yoghurt and porridge all add fluid
- Tea, coffee and milk count too. Moderate caffeine doesn't dehydrate you overall
When you need more
- Hot or humid weather
- Exercise, especially longer or sweaty sessions
- Illness with fever, vomiting or diarrhoea
- Pregnancy and breastfeeding
Simple signs you're drinking enough
For most healthy people, thirst is a good guide. Pale yellow urine is another easy check. Dark yellow urine, headaches, tiredness and dizziness can all be signs you need more fluid.
Water and appetite
Mild thirst is sometimes mistaken for hunger. If you want a snack soon after eating, try a glass of water first and see if the craving passes. Choosing water over sugary drinks is also one of the simplest ways to cut calories without changing what you eat.
If you have a heart or kidney condition, or take medicine that affects fluid balance, ask your doctor how much you should be drinking.
This article is general information, not medical advice. If you have a health condition or specific dietary needs, talk to a doctor or registered dietitian.
