Keeping hydrated

Expert reviewer Mr Paul McArdle, Registered Dietitian
Next review due November 2020

You can’t survive without water. It makes up nearly two-thirds of your body and is essential for you to function properly. Water has a wide range of benefits for your body – everything from removing waste products in urine to lubricating your joints. It can even make your skin look good.

Here, we explain why you need to drink enough and offer some tips to help you stay hydrated.

Glasses of water with fruit

How much should I drink?

As a basic guide, most people need about 1.5 to 2 litres of fluid a day, which is about eight to 10 glasses.

You can get this from water and other drinks, such as milk and fruit juice. Water in food also counts – fruit and vegetables contain lots of water. Cucumber and lettuce have the highest water content of any food – a massive 96%.

Tomatoes area also packed with water – about 94%. Keep your hydration levels topped up by adding them to a salad or a sandwich.

The exact amount of fluid you personally need can depends on things like:

  • your age – this affects how well your body is able to balance water and salts, and as you get older you store less water 
  • the amount of physical activity you do – you need to drink more if you exercise more 
  • the climate – you need to drink more if it's hot and you're sweating water out of your body 
  • if you’re pregnant – you’re more likely to develop constipation during pregnancy so you need to drink more 
  • your diet – if you’re following a special diet or very low-calorie diet, you need to drink more

What should I drink?


Water is the best choice when it comes to meeting your body's needs for fluids. It doesn't have any calories and is free if you drink tap water.

If you find it tough to drink just water and want a tastier drink, then squash, milk, fruit juices or teas will also top up your fluid levels. It's a trade-off though, because these contain calories, usually from sugar, and they can damage your teeth.

‘One way to make water more exciting is to add slices of lime, orange or lemon. Cucumber is also nice. It gives the water a fragrance and taste that makes it much more interesting. It’s healthy, hydrating and homemade.’ Bianca Parau, Senior Specialist Dietitian at Bupa.

Coconut water

Coconut is becoming a popular drink these days and is another option for topping up your fluid levels. It's rich in the mineral potassium, and also contains sodium, chloride, and natural sugars. In some parts of the world, it's used to replace lost fluids to treat dehydration. It's also been reported to contain antioxidants. But remember those sugars, so don't drink too much of it.

Fruit juice and smoothies

Fruit juices and smoothies contain lots of vitamins. One glass (150ml) can make up one of your five portions of fruit and vegetables a day. But the downside is, they contain lots of sugar and can be acidic, both of which are bad for your teeth. Because of this, it’s best to limit how much fruit juice you drink and have it with a meal.

One way to dilute all that sugar is to blend fruits with water or ice. It's a healthier option than milk or yoghurt.

Smoothies and juicing

Top tips from Bianca Parau, Senior Specialist Dietitian at Bupa’s Cromwell Hospital.

  • Use crushed ice to thicken your smoothie rather than using yoghurt or milk. 
  • Water-rich fruits include grapes, watermelon, kiwi and oranges, so these are good to add to your mix. 
  • Water-rich vegetables for your green juices could include iceberg lettuce, cucumber and celery. 
  • You can also use herbal teas in your juices and smoothies – peppermint is my favourite. 

An infographic showing a smoothie recipe

Fizzy drinks

Fizzy drinks and squashes can contain more calories and sugar than you would imagine. Some fizzy drinks contain the equivalent of a whopping 12 teaspoons of sugar. If you still decide to opt for these, choose squashes with ‘no added sugar’ on the label or low-calorie versions of fizzy drinks.


Milk is a good choice as it contains nutrients such as protein, B vitamins and calcium, as well as being a source of water. Be careful with how much you drink though, because it can also contains saturated fat. Choose semi-skimmed or skimmed options.

If cow's milk doesn't agree with you, soya, rice and almond milk are alternative healthy options. Some are fortified with calcium to ensure you don't miss out on this vital nutrient.

Tea and coffee

Tea, the nation's favourite, as well as coffee, also contribute to your fluid intake. Both contain caffeine, which is a mild diuretic so it can increase the amount of urine you produce. As long as you drink caffeinated drinks in moderation, you shouldn’t need to drink extra fluid to compensate for this. Limit yourself to 400mg of caffeine a day, which is about three cups of coffee or four cups of tea. Pregnant women should stop at 200mg a day. If you want more, drink herbal teas or decaffeinated versions.

Does alcohol count?

Although technically, alcoholic drinks contain water, they are also diuretics and make you lose water from your body as urine. You can become dehydrated if you drink too much alcohol. It's a good idea to drink water or other soft drinks alongside alcohol and to drink sensibly.

Is bottled best?

Bottled water is nutritionally no different from tap water. Tap water is safe to drink in the UK. However, if you’re abroad and unsure about the quality of the water or aren’t used to it, it’s usually best to stick to bottled water.

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Why is water important?

Your body uses water to help with many different processes, including:

  • transporting nutrients and oxygen around your body
  • getting rid of waste products
  • controlling your temperature
  • the function of your digestive system

Drinking enough water will also help to keep your skin healthy.


It’s important to keep your body’s water content topped up, otherwise dehydration can develop. This is a lack of water in your body that occurs when you lose more water than usual, such as through vomiting or diarrhoea, or you don’t drink enough, perhaps because you’re ill. Other causes for dehydration include sweating a lot or drinking too much alcohol.

So, how can you tell if you're dehydrated or not? One of the best indicators is the number of times you pass urine and its colour – it should be pale yellow. If you don’t need to go as often as usual, you only pass a small amount each time and it's dark in colour, it’s likely that you’re dehydrated. Other signs include:

  • having a headache
  • feeling tired and weak
  • confusion
  • mood swings
  • dry lips

Image showing hydration level by urine colour

What should I do if I become dehydrated?

If you think you may be dehydrated, you need to rehydrate your body by drinking fluid. For mild dehydration, drinking water may be all that’s needed – it’s better to drink little and often rather than trying to drink a lot all in one go as this may make you vomit, meaning that you lose even more water.

If you have more severe dehydration caused by diarrhoea or vomiting, you will also be losing important salts and sugars from your body. Rehydration sachets, which you add to water or other drinks, are a good way of replacing these. Some people choose sports drinks but these contain much more sugar than you need so it’s best to stick to rehydration sachets.

For more severe dehydration, seek urgent medical advice from your GP or pharmacist. You may need to go to hospital to be given fluids through a drip.

Can you drink too much water?

You might have heard stories about people drinking too much water and it's certainly possible. Drinking too much isn't good for you and can even be dangerous (although it rarely is). The reason it can be dangerous is that it can cause the level of salt in your blood to drop too low – a condition called hyponatraemia.

A good way to gauge if you're drinking the right amount is to check how often you're going to the toilet. If you're going lots and your urine looks really pale, you might be drinking more than you need.

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  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, November 2017
    Expert reviewer Mr Paul McArdle, Registered Dietitian
    Next review due November 2020