We lose water from our body throughout the day through natural processes such as sweating and going to the toilet. Hydration is the replacement of this water. 

Our bodies need water for a wide variety of functions including regulating body temperature, being physically active and brain function - so it’s important to ensure we are drinking the right amount of water to stay healthy. 

It’s crucial that we know how much fluid we need to stay healthy, what drinks are the best for hydration and why/when our fluid intake requirements may change. 

‘Fluid’ includes not only water from the tap or in a bottle, but also other drinks such as tea, coffee, milk, fruit juices and soft drinks. 

Water is essential for life! Water makes up, on average, 60% of bodyweight in men and 50-55% in women (because women have more body fat) and plays many different roles in the body including removing waste products in urine and acting as a lubricant and shock absorber in joints. 

If we do not drink enough fluid, over time we become dehydrated. Studies have shown that even low levels of dehydration (1-4%) can cause symptoms like headaches and poor concentration. 

When we are dehydrated, the kidneys reduce how much water we lose in the urine. This means that the colour of the urine becomes darker, and our urine colour can give us an idea of whether we are well hydrated. If we are drinking enough, our urine should be a straw or pale-yellow colour. If it is darker then we probably need more fluid. 

Thirst kicks in when the body is already a little dehydrated, so it’s important to drink when we are thirsty. However, in older adults the thirst response may be weaker and young children may not be able to tell others they are thirsty and so these groups are more at risk of dehydration and need support to drink regularly.

The amount of fluid we need depends on many things including the weather, how much physical activity we do and our age. It’s recommended we drink about 6-8 glasses of fluid per day. If the weather is hot or we are exercising, we need to drink more. 

We can get water from nearly all fluids that we drink, although alcoholic drinks don’t count towards your fluid intake as they can make you urinate more than usual.

The amount of fluid a child needs depends on many factors including their age, their sex, the weather and how much physical activity they do but generally they should aim to drink about 6-8 glasses of fluid per day (on top of the water provided by food in their diet). We do not have specific recommendations in the UK for how much fluid children should get in a day, but based on guidance from the EU, younger children need relatively smaller drinks (such as a 120–150ml serving) and older children need larger drinks (such as a 250–300ml serving).

Infants and young children have a higher proportion of body water than adults. They are also less heat tolerant and more likely to get dehydrated, especially if it’s hot and they are being active. 

It’s a good idea for anyone caring for children to make sure that water is available throughout the day, to include drinks with meals and snacks, and to encourage children to drink regularly. 

We have Healthy Hydration Guides for children aged 1-4 years and children aged 5-11 years available to download.

Babies that are fully breastfed get all the fluid they need from breastmilk. Formula-fed babies may need some extra water in hot weather – note that water for babies under 6 months should be boiled and cooled first.

Children aged 1-2 years will be getting most of the nutrients they need from solid foods, but breastfeeding can continue alongside this. The World Health Organization (WHO) recommends breastfeeding alongside appropriate complementary foods up to two years of age or beyond.

All non-alcoholic drinks can hydrate us and drinks such as fruit juices and milk also contain essential vitamins and minerals. However, some drinks, such as soft drinks, can be high in sugars. Drinking a lot of sugary drinks is linked with risk of type 2 diabetes and weight gain in both children and adults.

Physical activity increases the amount of fluid we need to replace the water we lose as sweat. The extra fluid we need depends on how long we are active, how intense the activity is and whether it’s hot and humid. It’s a good idea to start any physical activity well hydrated and to drink at intervals during activity. Water is fine for rehydration after moderate exercise and most active people do not need special sports drinks to stay hydrated. However, for high intensity exercise that lasts more than 1 hour or so, drinks that contain some sugars and sodium (salt), such as sports drinks or homemade versions, may be better at replacing the extra fluid lost as sweat.

As well as staying hydrated, it’s also important to look after our teeth. Consuming sugary drinks too often can harm our teeth. If consumed often, some drinks, such as fizzy drinks and fruit juices are acidic and this can cause dental erosion (damage to tooth enamel).

What are the best drinks for children?

Water and milk are the best drinks for children as they do not contain free sugars. Drinking sugary drinks too often can also lead to tooth decay, especially if consumed often between meals or if teeth are not brushed regularly with fluoride toothpaste.

Higher consumption of sugary drinks has been linked with weight gain in children.  Some drinks like milk and fruit juice provide vitamins and minerals. However, fruit juice also contains ‘free sugars’ (this means sugar which has been added to a drink) so they should not be consumed in large amounts.

Drinks such as tea, coffee and some soft drinks may also contain caffeine which is a mild stimulant. Preschool children should not be given drinks containing caffeine and these should be limited in younger children. Caffeine may affect children’s sleep if consumed close to bedtime. Energy drinks containing high amounts of caffeine are not suitable for children.

For more information about drinks for children our Healthy Hydration Guides for children aged 1-4 years and children aged 5-11 years can be downloaded

The first steps to ensuring you stay hydrated are knowing how much you should be drinking, when you need to up your fluid intake and how to spot the signs if you become dehydrated. These are all outlined in the sections above.

It's also a good idea to create good habits around the fluids you drink so staying hydrated becomes a part of your daily life. For example, taking a water bottle with you wherever you go - you can now fill it up for free at most cafes and restaurants!

Although for adults taking steps to improve your hydration may be straightforward, it can be harder to ensure the children or older adults you care for are getting enough fluids. 

If you are caring for an older person who is in poor health and/or has mobility issues, then it’s important to make sure drinks are available at all times and to provide help with drinking if needed. The fear of incontinence can mean that people restrict their fluid intakes.

Good hydration is important because it can help prevent constipation, urine infections and falls. As we get older our sense of thirst may reduce so it’s especially important to ensure they are drinking regularly throughout the day. 

If an older person has a poor appetite or you are worried about them losing weight, you may also want to encourage them to choose drinks that provide energy and nutrients as well.

For more information, see our article on dehydration in older people.