How much water should I drink a day? UK guidance

The NHS says to aim for 6 to 8 cups or glasses of fluid a day, which is about 1.2 litres. Tea, coffee and lower-fat milk count, and you need more when it's hot, when you train for a long time or when you're unwell. You've heard eight glasses, two litres and three litres; the UK guidance is simpler than most of what you'll read online.

In short

The NHS says to aim for 6 to 8 cups or glasses of fluid a day. It's a guide, not a strict rule.

It doesn't all have to be water. Tea, coffee, lower-fat milk and sugar-free drinks count too.

Drink more when it's hot, when you're active for a long time, or when you're unwell. Pale yellow pee is a good sign.

1. How much water should I drink a day in the UK?

The NHS says the government recommends you aim to drink 6 to 8 cups or glasses of fluid a day. It describes this as "just a guide".

The British Nutrition Foundation (BNF) puts that at roughly 1.2 litres a day: six 200 ml glasses or eight 150 ml glasses.

That's less than the "two litres a day" you often hear. The difference is explained below.

2. Why do some people say 2 litres?

Because that figure usually includes the water in your food as well as your drinks.

The European Food Safety Authority (EFSA) sets "adequate intakes" for total water, from food and drink together. The BNF quotes them as:

Women: 2.0 litres a day
Men: 2.5 litres a day

These assume a temperate climate and moderate activity. EFSA assumes about 20% of that water comes from food, such as fruit, vegetables, soups and yoghurt, and about 80% from drinks.

So the UK's 6 to 8 glasses and EFSA's 2 to 2.5 litres aren't really in conflict. They're measuring slightly different things.

3. How big is a glass?

Glasses vary a lot, which is why the guide is a range. The BNF works it out as six 200 ml glasses or eight 150 ml glasses, both about 1.2 litres.

Some everyday comparisons, worked out by us:

Container	Roughly
Small glass	150 ml
Standard glass or mug	200 to 250 ml
Typical water bottle	500 ml, about two and a half 200 ml glasses
Large reusable bottle	750 ml to 1 litre

So two and a half refills of a 500 ml bottle gets you to the guide. A large reusable bottle filled once or twice does the same.

4. Does tea and coffee count towards my water?

Yes.

The NHS says water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count towards your daily intake. The BNF adds that moderate amounts of tea and coffee don't appear to affect how hydrated you are.

If you're pregnant, the BNF notes the advice to keep caffeine to 200 mg a day.

Things to watch:

Fruit juice and smoothies count, but they're high in sugar. The NHS says to have no more than one small glass (150 ml) a day, with a meal.
Sugary fizzy drinks count as fluid, but the NHS suggests swapping them for diet, sugar-free or no-added-sugar versions.

5. When should I drink more?

The NHS lists times when you may need more fluid, including when you're:

in a hot environment
physically active for long periods
pregnant or breastfeeding
unwell

The BNF adds that people doing strenuous activity, or living somewhere hot or humid, may need more than the standard guide. It also gives extra amounts for pregnancy (about 300 ml more a day) and breastfeeding (about 700 ml more).

If you've been sweating from exercise, the NHS says to drink extra fluids.

6. How do I know if I'm drinking enough?

Check the colour of your pee. It's the simplest test there is.

The NHS says to drink enough during the day so that your pee is a pale colour. On its water page, it describes this as a clear, pale yellow.

Dark yellow pee is a sign you may need to drink more.

7. What are the signs of dehydration?

The NHS lists these symptoms of dehydration in adults:

feeling thirsty
a headache
feeling dizzy or light-headed
feeling tired
a dry mouth, lips and tongue
sunken eyes
dark yellow, strong-smelling pee
peeing less often than usual

Usually, drinking more fluids is enough to sort it out.

When to get help

The NHS says to see a GP or call NHS 111 urgently if, for example, you feel unusually tired, you're dizzy when you stand up and it doesn't go away, your pee is still dark yellow or you're passing less than normal, or you're breathing quickly or have a fast heartbeat.

Call 999 or go to A&E for signs such as confusion, difficulty breathing, cold or blotchy skin, or unusual sleepiness. If you're unsure, NHS 111 can advise.

8. Who is more at risk of dehydration?

The NHS says anyone can become dehydrated, but some people are more at risk, including:

babies, children and older adults
people with diabetes
people who've been vomiting or have diarrhoea
people who've been in the sun or heat too long
people who've drunk a lot of alcohol
people who sweat heavily during exercise
people with a high temperature
people taking diuretics ("water tablets")
people who rely on others to bring them drinks

If you care for an older relative, the BNF notes that older adults who are unwell may need support to drink regularly.

If you have a heart, kidney or other medical condition and have been told to limit fluids, follow your doctor's advice rather than general guidance.

9. How can I drink more without thinking about it?

A few simple habits, from us rather than the NHS:

Start with a glass when you get up.
Have a drink with every meal. That's three glasses already.
Keep a bottle on your desk where you can see it.
Drink before, during and after exercise, especially in warm weather.
Tie it to things you already do, such as a glass every time you make a cup of tea for someone else.
Eat water-rich food, such as fruit, salad and soup.

Don't force down huge amounts at once. Steady sips through the day are easier.

Do I need an app to track water?

Most people don't need an app to drink enough. Pale pee and a bottle on the desk will do it.

An app can help if you're the sort of person who looks up at 4pm and realises you haven't had a drink since breakfast. Some free ways to keep track:

A marked bottle, with times or lines on the side.
A paper tally on the fridge: one tick per glass.
A repeating reminder on your phone at a few set times a day.

How Reptyl helps

Reptyl Water keeps track of how much you drink today, and nothing else.

One tap per drink. Log a glass or a bottle in a second, or any amount you like.
Your own goal. Set the amount that suits you, such as 6 to 8 glasses, or more on training days. The screen turns lime when you reach it.
Reminders, if you want them. They're off until you turn them on. They skip times just after a drink and stop once you hit your goal.
See the week. The last 7 or 30 days as a simple chart.

It's a one-off purchase with no subscription, no account and no adverts, and your data stays on your phone. The Water page has the details. A marked bottle works just as well.

For food, see how much protein you need and how to count calories without paying for an app.

Quick answers

Is 2 litres of water a day too much?

For most healthy adults, no. EFSA's figures of 2.0 litres for women and 2.5 litres for men include water from food as well as drinks. The NHS guide for drinks alone is 6 to 8 glasses. If you've been told to limit fluids for a medical reason, follow that advice.

Does coffee dehydrate you?

The BNF says moderate amounts of tea and coffee don't appear to affect hydration, and the NHS counts them towards your daily fluid.

Does sparkling water count?

Yes. The NHS counts water towards your daily fluid, and that includes sparkling. Flavoured sparkling drinks may contain sugar, so check the label.

Should I drink more water when I exercise?

Yes. The NHS says to drink extra fluids if you've been sweating from physical activity, and more when you're active for long periods or it's hot.

Want a one-tap water tracker? See Reptyl Water