How Much Water Should You Drink a Day? UK NHS Guidance for 2026

Quick answer

The NHS recommends drinking 6 to 8 cups or glasses of fluid a day. In practical terms that is about 1.5 to 2 litres, though the exact figure depends on your size, how active you are, the weather and your health.

Crucially, that total is not all plain water. The NHS counts water, lower-fat milk, sugar-free drinks, and even tea and coffee towards your daily fluid intake. So if you have a couple of mugs of tea, a glass of milk on your cereal and a few glasses of water through the day, you are already most of the way there.

What the NHS actually says

The Eatwell Guide — the UK government's official model of a healthy diet — advises 6 to 8 glasses of fluid every day. That is the headline number you will see repeated across NHS pages, and it is deliberately given as a range rather than a single rigid figure, because real fluid needs vary a lot from person to person and day to day.

A few points the NHS makes that often get lost:

• Water, lower-fat milk and sugar-free drinks (including tea and coffee) all count.
• Fruit juice and smoothies count too, but should be limited to a combined 150 ml a day because of the free sugars they contain.
• Food provides fluid as well — soups, stews, fruit and vegetables can supply a meaningful share of your daily intake, which is one reason the "8 glasses of pure water" myth overstates how much plain water you really need to pour.

The old idea that you must drink eight large glasses of water on top of everything else has no strong evidence behind it. The NHS figure already bakes in the drinks you have anyway.

Does tea and coffee really count?

Yes. This surprises people because caffeine is a mild diuretic — it makes you produce a little more urine. But the volume of fluid in a normal cup of tea or coffee far outweighs the small extra amount you pass, so on balance these drinks still hydrate you.

The practical advice: tea and coffee in moderation are fine and contribute to your total, but plain water, lower-fat milk and sugar-free drinks are kinder to your teeth and don't add caffeine or, in many shop-bought coffees, a lot of sugar and calories. If you are tracking what you eat and drink, those milky, syrupy coffees can quietly add a few hundred calories — something our calorie calculator can help you put into context against your daily energy needs.

How body weight and activity change your needs

The 6-to-8-glasses figure is a sensible default for an average adult in a temperate UK climate doing light activity. Two things push your needs up.

Body size

A larger body has more tissue to keep hydrated and generally loses more water through breathing and sweating. A rough rule of thumb some people use is around 30 to 35 ml of fluid per kilogram of body weight. For an 80 kg adult that lands at roughly 2.4 to 2.8 litres a day including all sources — comfortably within the range you would expect from normal eating and drinking.

Treat that formula as a ballpark, not gospel. It ignores activity, climate and health, and the NHS does not promote a per-kilogram rule precisely because urine colour and thirst are better real-time guides. If you want a reference point for a healthy weight to plug into that kind of estimate, the BMI calculator and ideal weight calculator give you NHS-aligned figures to work from.

Activity and heat

Exercise and hot weather are the big multipliers. You can lose 0.5 to 2 litres of sweat per hour during hard exercise in the heat. For most everyday workouts the simple approach is:

• Drink normally through the day.
• Have a glass of water before you start.
• Sip during exercise if it lasts longer than 30 to 45 minutes.
• Rehydrate afterwards until your urine returns to pale straw.

For long endurance events lasting several hours, electrolytes (especially sodium) start to matter as well as plain water — which we will come back to under over-hydration.

Times you need more fluid

The NHS flags several situations where you should consciously drink more than usual:

• Hot weather or a heated indoor environment.
• During and after physical activity.
• When you have a fever, are vomiting or have diarrhoea — these cause rapid fluid loss and are the most common everyday cause of dehydration, especially in young children and older adults.
• Pregnancy and breastfeeding. Pregnant women are advised to drink plenty of fluids, and breastfeeding mothers need extra to support milk production.
• Older age. The sense of thirst weakens with age, so older people can become dehydrated without feeling especially thirsty. Drinking to a routine rather than waiting for thirst helps.

How to tell if you are drinking enough

You do not need to count millilitres. Two free, reliable checks:

1. Urine colour

This is the single most useful indicator. Aim for pale straw or light yellow. Dark yellow or amber urine that is strong-smelling usually means you need to drink more. (Some vitamin supplements, especially B vitamins, can turn urine bright yellow — that is harmless and not a hydration signal.)

2. Thirst

Thirst is a decent guide for most healthy adults under normal conditions. Its main weaknesses are at the extremes: it lags behind during intense exercise, and it fades with age — which is exactly when people are most at risk.

Signs of dehydration to watch for

According to the NHS, signs of dehydration in adults and older children include:

• Feeling thirsty
• Dark yellow, strong-smelling urine
• Peeing less often than usual
• Feeling dizzy or lightheaded
• Feeling tired
• A dry mouth, lips and eyes

In babies and young children, look for:

• A sunken soft spot (fontanelle) on the head
• Few or no tears when crying
• Fewer wet nappies than usual
• Drowsiness or irritability

Mild dehydration is easily fixed by drinking fluids — water, or an oral rehydration solution if you have been ill with vomiting or diarrhoea. Seek urgent medical help if someone is very drowsy or confused, not passing urine, has a rapid heartbeat or breathing, or if a baby shows the signs above. These can indicate severe dehydration that needs treatment.

Can you drink too much water?

Yes, though it is uncommon. Drinking an extreme amount of water in a short space of time can dilute the sodium in your blood to dangerous levels — a condition called hyponatraemia ("water intoxication"). It mainly affects endurance athletes, such as marathon runners, who drink far more than they sweat out over many hours.

For everyday life this is not something to worry about. The safe approach is simple: spread your fluid across the day rather than forcing down litres in one go, and during long, intense exercise replace electrolytes as well as water.

Hydration, weight and your diet

People often confuse thirst with hunger, and a glass of water before a meal can take the edge off appetite. Swapping sugary drinks for water also removes a surprising number of calories from a typical week. If you are managing your weight, it is worth seeing how your drinks fit into your overall energy balance using the calorie calculator, and checking your healthy-weight range with the BMI calculator. Hydration alone will not transform your weight, but cutting liquid calories is one of the easiest wins there is.

A simple daily plan

If you want a routine rather than a number to hit:

1. A glass of water when you wake up.
2. A drink with every meal — water, milk or a sugar-free option.
3. A mug of tea or coffee or two through the day (these count).
4. A glass of water with any exercise, plus more afterwards.
5. Keep a refillable bottle on your desk or in your bag as a visual nudge.
6. Check your urine colour once or twice a day and top up if it is dark.

Do that and you will almost certainly land inside the NHS's 6-to-8-glasses range without thinking about it.

Frequently asked questions

How much water should I drink a day according to the NHS? Six to eight cups or glasses of fluid a day, roughly 1.5 to 2 litres. That total includes water, lower-fat milk, sugar-free drinks, tea and coffee. Drink more in hot weather, during exercise, in pregnancy, and when ill.

Does tea and coffee count towards my daily fluid intake? Yes. The NHS counts them. The diuretic effect of normal amounts of caffeine is outweighed by the fluid in the drink, so they still hydrate you on balance.

Should I drink more water based on my body weight? Larger and more active people do need more, and around 30 to 35 ml per kg is a rough guide. But it is not a strict formula — urine colour is a better day-to-day check.

What are the signs of dehydration? Thirst, dark and strong-smelling urine, peeing less, dizziness, tiredness and a dry mouth. In babies, watch for a sunken soft spot, few tears and fewer wet nappies.

Can you drink too much water? Yes, but rarely. Drinking huge amounts very quickly can cause hyponatraemia. For normal life, spreading fluid across the day is safe.

Sources

• NHS: Water, drinks and your health
• NHS: Dehydration
• NHS / Public Health England: The Eatwell Guide

This article is general information, not medical advice. If you have a health condition that affects how much fluid you should drink — such as kidney disease or heart failure — follow the advice of your GP or specialist.