What the common guidance says
Recommendations vary a little depending on who you ask, but they land in a similar place:
- The NHS suggests aiming for around 6 to 8 cups or glasses of fluid a day, and notes that water, lower-fat milk and sugar-free drinks, including tea and coffee, all count.
- The US National Academies describe an adequate total water intake of roughly 2.7 litres a day for women and 3.7 litres for men. Importantly, that is total water from all drinks and food, and food typically provides around a fifth of it.
- The European Food Safety Authority gives similar figures of around 2.0 litres a day for women and 2.5 litres for men, again from both drinks and food.
These are general reference amounts for healthy adults in mild conditions, not strict targets. Your own needs may be higher or lower.
What changes how much you need
| Factor | Effect on needs | What to do |
|---|---|---|
| Hot or humid weather | More fluid lost through sweat | Drink more often, before you feel very thirsty |
| Exercise | Sweat loss rises with duration and intensity | Drink before, during and after longer sessions |
| Body size | Larger bodies generally need more | Use thirst and urine colour as a guide |
| Illness with fever, vomiting or diarrhoea | Higher fluid and salt losses | Sip fluids; seek medical advice if severe |
| Pregnancy and breastfeeding | Needs are higher | Follow advice from your midwife or doctor |
| Older age | Thirst sensation can be weaker | Drink regularly rather than waiting for thirst |
What counts toward your total
Plain water is the simplest choice: it has no calories or sugar. But it is not the only thing that counts.
- Milk and plant milks provide fluid along with protein and other nutrients.
- Tea and coffee count. Caffeine has a mild diuretic effect, but for regular drinkers, moderate amounts still contribute to hydration overall.
- Sugar-free and flavoured waters count and can help if you find plain water boring.
- Fruit juice and smoothies count, but contain free sugars; the NHS suggests limiting them to a small glass (150 ml) a day combined.
- Sugary soft drinks provide fluid but also a lot of sugar with little else, so they are best kept occasional.
- Food contributes too: fruit, vegetables, soups, yoghurt and cooked grains all contain water.
Alcohol is not a good way to hydrate, as it increases fluid loss.
Simple signs you are drinking enough
For most healthy adults, the body is good at regulating fluid, and thirst is a reliable signal. Two easy checks:
- Urine colour. Pale straw or light yellow usually suggests you are well hydrated. Dark yellow or amber is a sign to drink more. Some vitamins and foods can change colour, so this is a rough guide.
- Thirst. Feeling thirsty is a cue to drink. If you are rarely thirsty and urine is pale, you are probably fine.
Common signs of mild dehydration include thirst, dark urine, tiredness, dizziness, headache and a dry mouth. If these persist despite drinking, see a doctor.
Can you drink too much?
It is possible, though uncommon in everyday life. Drinking very large amounts in a short time, which sometimes happens during endurance events, can dilute sodium levels in the blood, a condition called hyponatraemia, which can be dangerous. Drinking to thirst and not forcing large volumes is a sensible approach. Some people, including those with certain heart, kidney or liver conditions, are advised to limit fluids. If that applies to you, follow your doctor's guidance rather than general recommendations.
Habits that make it easier
- Keep a water bottle within reach at your desk or in your bag.
- Have a glass of water with each meal.
- Add slices of lemon, cucumber or mint if you prefer some flavour.
- Eat plenty of water-rich foods such as fruit, vegetables and soups.
- Drink a little more on hot days and when you exercise.
Water, energy and appetite
Even mild dehydration is linked to tiredness and poorer concentration for some people, so keeping hydrated is part of feeling your best. Some people also mistake thirst for hunger. Our guide to foods for steady energy covers other everyday habits linked to feeling more even through the day.
Frequently asked questions
Is 8 glasses of water a day right for everyone?
It is a useful rule of thumb, and the NHS suggests about 6 to 8 cups or glasses of fluid a day. Your needs may be higher in hot weather, during exercise, or if you are larger, and lower if you are advised to limit fluids.
Do tea and coffee count toward water intake?
Yes. For regular drinkers, moderate amounts of tea and coffee contribute to fluid intake, according to common guidance such as the NHS.
How can I tell if I am dehydrated?
Thirst, dark yellow urine, tiredness, headache and a dry mouth are common signs. Pale straw-coloured urine usually suggests you are drinking enough. See a doctor if symptoms persist.