How Much Water Should You Drink a Day? The NHS Guide

Ask five people how much water you should drink and you'll get five confident answers, usually involving a very large bottle. The official advice is a lot more relaxed than the social media version, and it's worth knowing what it really says.

I've pulled this together from the NHS pages on water, drinks and dehydration. It's general information for healthy adults. If you have a medical condition, take medicines that affect fluids, or you're caring for a baby or an older person, your GP or pharmacist can give advice that fits.

The official daily fluid guide for adults

The NHS, quoting government advice, says to aim to drink 6 to 8 cups or glasses of fluid a day. It's presented as a guide, not a target you have to hit exactly. Notice the word fluid: the number covers more than plain water.

The NHS also says you get some fluid from food, so you're not relying on drinks alone.

What counts towards your fluid intake

According to the NHS, water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count. That surprises people who've been told coffee doesn't count. The NHS only asks you to take caffeine in moderation, because sensitivity varies, and to check the label on high-caffeine drinks.

• Water: the NHS describes it as the best way to replace fluids you've lost.
• Lower-fat milk: counts as fluid.
• Tea and coffee: count, in moderation.
• Fruit juice and smoothies: the NHS says limit these to one small glass of 150 millilitres a day, with a meal, because they're high in sugar.
• Sugary drinks: the NHS suggests adults swap them for diet, sugar-free or no-added-sugar versions.

A simple way to check you're drinking enough

You don't need an app or a marked bottle to keep track, and you don't need to count every sip. The NHS suggests aiming to drink enough during the day that your pee is a clear pale yellow. If it's darker than that, it's worth having a drink.

Drinking with meals, keeping a glass or bottle in sight and having a drink when you wake up are easy habits for spreading fluid through the day. These are ordinary habit tips rather than NHS rules, so use whatever suits your routine.

When you may need more fluid than usual

The NHS says your needs are higher if you're:

• pregnant or breastfeeding
• in a hot environment
• physically active for long periods
• ill, or recovering from illness

It also advises drinking extra if you've been sweating from exercise or you're unwell. Water is its recommended way to replace lost fluids. If you're being sick or have diarrhoea and are losing a lot of fluid, the NHS suggests asking a pharmacist about oral rehydration solutions.

Signs you might be dehydrated

The NHS dehydration page lists these symptoms for adults and children:

• thirst, and a dry mouth, lips and tongue
• headache, light-headedness or dizziness
• dark yellow, strong-smelling pee, or peeing less often
• tiredness and sunken eyes

The NHS says babies, children and older adults are at greater risk, and so are people with diabetes, a high temperature, heavy sweating, heavy drinking or those taking diuretic medicines. It also advises avoiding caffeine and alcohol when you're dehydrated, as they can make it worse.

When dehydration needs medical help

Most mild cases can be sorted with fluids, but the NHS is clear about warning signs. It says to get an urgent GP appointment or call NHS 111 for things such as unusual tiredness, dizziness on standing that doesn't go away, fast breathing or a fast heart rate, and it says to call 111 for advice on any child under 5.

Call 999 or go to A&E if there's blue, grey, pale or blotchy skin, lips or tongue, cold skin, difficulty breathing, confusion, or being sleepier than normal or hard to wake. The NHS says not to drive yourself to A&E in that situation.

Water, food and the bigger picture of healthy eating

Fluid is one part of eating well. The fuller picture also includes how carbohydrates affect you, and my guide to the glycemic index and how it rates carbohydrate foods is a good place to start. Sugary drinks are a good example of how the two ideas meet. The NHS says to swap them for sugar-free versions and limit fruit juice.

Hydration is one habit among many, so it helps to look at your whole routine, from what you drink to what you eat across the week. The same goes for vitamins and minerals, where a balanced diet does most of the work. I've covered what micronutrients are and where to find them in a separate explainer.

Sharing what you know about hydration and nutrition

If you're a dietitian or registered nutrition professional who can cut through hydration myths, there's a real audience for it.

If you're a registered nutrition professional, here are nutrition publications open to contributors.

Frequently asked questions

Is 8 glasses of water a day a rule?

No. The NHS, quoting government advice, says to aim for 6 to 8 cups or glasses of fluid a day as a guide, and that includes drinks other than plain water.

Do tea and coffee count towards my fluid?

Yes. The NHS says water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count. It asks you to have caffeine in moderation.

How can I tell if I'm drinking enough?

The NHS suggests aiming for pee that's a clear pale yellow. Darker pee is a sign to drink more.

Do I need more fluid when it's hot or when I exercise?

Yes. The NHS says needs are higher in a hot environment, when you're active for long periods, when you're ill, and if you're pregnant or breastfeeding.

What are the symptoms of dehydration?

The NHS lists thirst, a dry mouth, headache, dizziness, dark yellow strong-smelling pee, tiredness and sunken eyes. Call 111 or see a GP if they don't ease, and use 999 for the emergency signs it describes.