What Are the Benefits of Drinking Water? How Much Water Do You Need?

Created: 16.01.2023 · Last Updated: 19.08.2026 · Category: Nutrition and Diet · Prepared by the Academic Hospital Web and Editorial Board.

Why Is Water Important?

Water is essential for human life. It supports cellular function, transport of nutrients and other substances, regulation of body temperature and removal of metabolic waste.

The body continuously loses water through urine, perspiration, breathing and bowel movements. Replacing these losses through beverages and food helps maintain normal fluid balance.

How Much of the Body Is Water?

Water is the largest single constituent of the human body, but the proportion of body water is not the same in everyone.

It varies according to age, sex, body composition and the relative amounts of fat and lean tissue.

Infants generally have a higher proportion of body water. The proportion changes with growth, ageing and changes in body composition.

There is no single ideal body-water percentage that applies to everyone. Hydration should not be assessed from one body-composition percentage alone.

What Are the Benefits of Drinking Water?

Adequate fluid intake supports normal body function.

Water helps the body:

  • Maintain normal body temperature,
  • Lubricate and cushion joints,
  • Transport nutrients and other substances,
  • Remove waste through urine and other pathways,
  • Support normal bowel function,
  • Prevent dehydration.

Dehydration can contribute to difficulty thinking clearly, mood changes, overheating, constipation and an increased risk of kidney stones in some people.

How Much Water Do You Need Each Day?

There is no single daily amount that is appropriate for everyone.

Fluid requirements vary with age, body size, activity level, climate, diet, pregnancy, breastfeeding and medical conditions.

The European Food Safety Authority considers an adequate total daily water intake for adults to be approximately:

  • 2.0 litres for women,
  • 2.5 litres for men.

These figures refer to total water from drinking water, other beverages and food, not simply glasses of plain water.

The U.S. National Academies uses different population data and reports adequate total water intakes of approximately 2.7 litres per day for adult women and 3.7 litres for adult men.

There is no universal rule that everyone must drink exactly 2–2.5 litres of plain water every day. Individual needs vary considerably.

Does All Water Have to Come From Drinking Water?

No. Total water intake comes from drinking water, other beverages and the moisture naturally contained in food.

Fruit, vegetables, soups, yoghurt and many other foods contribute to daily water intake.

Plain water remains an excellent primary beverage because it hydrates without adding calories. Replacing sugar-sweetened drinks with water can also reduce overall calorie intake.

When Do Water Needs Increase?

You may require additional fluids when:

  • The weather is hot,
  • You are physically active or sweating heavily,
  • You have a fever,
  • You have diarrhoea,
  • You are vomiting,
  • You are pregnant or breastfeeding.

What Are the Signs of Dehydration?

Dehydration occurs when fluid losses are greater than fluid intake.

Possible signs include thirst, dry mouth, reduced urination, dark urine, fatigue, dizziness, headache and difficulty concentrating.

Marked confusion, fainting, very little or no urine, severe weakness or persistent vomiting that prevents fluid intake requires medical assessment.

What Does Urine Colour Tell You About Hydration?

Urine colour can provide a practical clue about hydration.

Pale yellow urine is generally consistent with adequate fluid intake, while dark yellow urine may suggest that more fluid is needed.

However, medicines, vitamins, foods and certain medical conditions can also change urine colour, so it should not be used as a diagnostic test on its own.

Can Drinking Water Reduce the Risk of Kidney Stones?

Adequate fluid intake is one of the most important lifestyle measures used to help prevent kidney stones, particularly in people who have previously developed stones.

Drinking enough fluid helps keep urine diluted and reduces the concentration of minerals that can contribute to stone formation.

People with a history of kidney stones may require individual fluid targets depending on stone type, kidney function and other medical factors.

Can Drinking Water Help With Constipation?

Adequate hydration supports normal bowel function, and dehydration can contribute to constipation.

However, constipation can also be related to fibre intake, physical activity, medications, bowel disorders and other medical conditions.

Drinking additional water alone therefore does not treat every case of constipation.

Does Drinking Water Cause Weight Loss?

Water contains no calories. Replacing sugar-sweetened or high-calorie beverages with plain water can therefore help reduce daily energy intake.

However, water should not be described as a treatment that directly burns fat or guarantees weight loss.

Weight management requires an overall approach that includes appropriate nutrition, physical activity, sleep and other lifestyle factors.

Adequate hydration is important for health, but drinking water cannot be claimed to prevent loose skin or muscle cramps during weight loss on its own.

Can You Drink Too Much Water?

Yes. Although water is essential, drinking substantially more water than the body can excrete over a short period can occasionally be dangerous.

Excessive water intake can dilute blood sodium and lead to hyponatraemia.

The goal is therefore appropriate hydration, not drinking as much water as possible.

Who Needs Individual Advice About Fluid Intake?

Advice to simply “drink more water” is not appropriate for everyone.

Individual fluid targets may be necessary for people with:

  • Heart failure,
  • Advanced kidney disease or kidney failure,
  • Certain liver conditions,
  • Conditions affecting sodium or fluid balance,
  • Medical conditions requiring fluid restriction.

Daily Water Needs Are Individual

Age, activity level, climate, diet, pregnancy, breastfeeding and medical conditions can all affect fluid requirements. People with chronic medical conditions may need individualised advice.

Frequently Asked Questions

How much water should you drink each day?
There is no single amount that is appropriate for everyone. Water requirements vary according to age, body size, activity level, climate, diet and medical conditions. EFSA considers approximately 2.0 litres of total water per day for women and 2.5 litres for men adequate; these values include water from food and other beverages.
Does everyone need eight to ten glasses of water?
No. Eight to ten glasses can be used as a simple general guide, but it is not a fixed requirement for every person. Total water requirements vary according to individual circumstances.
Do tea and coffee count toward daily fluid intake?
Yes. The water in tea, coffee and other beverages contributes to total fluid intake. Plain water remains an excellent primary beverage because it provides hydration without calories.
Does dark urine mean you need more water?
Dark yellow urine can suggest that more fluid may be needed. However, medicines, vitamins, food and medical conditions can also affect urine colour, so it is not a diagnostic test on its own.
Can water help prevent kidney stones?
Adequate fluid intake helps dilute urine and is an important lifestyle measure for preventing kidney stones. People who have previously had kidney stones may need individual fluid targets based on stone type and medical status.
Does drinking water make you lose weight?
Water does not directly burn fat or guarantee weight loss. However, replacing sugar-sweetened or high-calorie beverages with water can help reduce overall calorie intake.
Can drinking too much water be harmful?
Yes. Drinking excessive amounts of water over a short period can occasionally dilute blood sodium to dangerous levels. The aim is appropriate hydration rather than drinking as much water as possible.
Should people with heart or kidney disease drink more water?
Not necessarily. People with heart failure, advanced kidney disease and certain other conditions may need to restrict fluid intake. Their daily fluid target should be determined by their healthcare professional.
Academic Hospital note: Daily fluid requirements cannot be determined by a single formula. People with kidney, heart or other conditions affecting fluid and electrolyte balance may require an individualised fluid plan. You can book an appointment.

References

  1. Academic Hospital. Benefits of Water
  2. European Food Safety Authority. Dietary Reference Values for Water
  3. National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Water
  4. Centers for Disease Control and Prevention. About Water and Healthier Drinks
  5. National Institute of Diabetes and Digestive and Kidney Diseases. Eating, Diet, & Nutrition for Kidney Stones

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