Drinking enough fluid is important for everyone. Not drinking enough can lead to dehydration, which may affect both physical and mental health. (Dehydration is the term used when the body lacks enough water to work properly.) This Food Fact Sheet will explain how much fluid you need and how to spot the signs of dehydration.
Water is essential for life and makes up a large proportion of the body. It has many important roles, including transporting nutrients in the blood, removing waste products through urine, regulating body temperature through sweating and lubricating joints.
Good hydration supports alertness and concentration, helps prevent constipation and is linked to a reduced risk of urinary tract infections, kidney stones and kidney damage. Repeated episodes of even mild dehydration may increase the risk of long-term kidney problems.
How much do I need to drink?
Drinks provide around 70–80% of your daily water needs. The remaining 20–30% comes from foods such as soups, stews, fruit and vegetables.
Recommended adequate intakes of water from drinks
| Age | Adequate water intake from drinks (ml/day) | |
| Infants | 7-12 months | 640 - 800ml |
| Children |
1-2 years 2-3 years 4-8 years 9-13 years More than 14 years |
880 - 960ml 1040ml 1280ml Boys: 1680ml Girls: 1520ml Same as adults |
| Adults including older people |
Men: 2000ml Women: 1600ml |
|
| Those who are pregnant | Same as adults + 300ml per day | |
| Those who are breastfeeding | Same as adults + 600-700ml per day |
Source: European Food Safety Authority (EFSA)
These are average values. Individual fluid needs vary depending on factors such as weather, indoor heating or air conditioning and physical activity. Hot weather and exercise increase fluid losses through sweat and increase how much fluid you need. Some medical conditions require people to follow strict fluid intake restrictions – this should only be advised by your doctor or dietitian.
How do I know if I’m drinking enough?
Thirst helps regulate hydration, but it is not always a reliable guide. You may stop feeling thirsty before your body is fully rehydrated.
Urine colour is a simple and useful indicator:
- Pale straw-coloured urine usually indicates good hydration
- Dark yellow urine often suggests dehydration
- Dehydration is common in older adults and can be difficult to detect, as thirst and urine colour may be unreliable. See our Hydration in Older Adults Fact Sheet for more information.
Regular urination is a good sign of hydration – for most adults, this means passing urine around four to eight times a day.
If you are concerned, seek advice from your GP.
Thirst is not a reliable indicator in children or older adults, so regular drinking should be encouraged. Well-hydrated infants and toddlers typically have regular wet nappies.
What happens if I don’t drink enough?
Not drinking enough fluids can lead to dehydration, which may cause:
- Headaches
- Tiredness
- Confusion
- Poor concentration
- Constipation
- Urinary tract infections (UTIs)
Some people are at higher risk of dehydration, including those who:
- Depend on others for drinks
- Have swallowing difficulties
- Have runny poo, vomiting or fever
- Are physically very active
- Avoid drinking due to limited toilet access
- Take certain medications
What types of drinks should I have?
All drinks contribute to hydration and what you choose depends on your preference, but healthy choices include:
- Water is one of the best options as it contains no calories or sugar
- Unsweetened tea and coffee, milk and milk alternatives also contribute to fluid intake
Infants
Infants should receive breastmilk or infant formula as their sole source of fluid until six months of age. From six months, small amounts of water can be offered between meals alongside continued breastfeeding or formula feeding. In hot weather, some formula-fed infants may require extra cooled boiled water.
Children
Water and milk are the best fluids for children as they do not contain free sugars that can contribute to tooth decay. Cow’s milk can be introduced as a main drink from one year of age. Calcium-fortified plant-based milk alternatives are not suitable as a main drink for infants under one year and should not be used before two years unless advised by a dietitian.
Sugary drinks (including fizzy drinks) should be limited. Fruit juice and smoothies provide fluid and nutrients but also contain free sugars, which can increase the risk of tooth decay. Limit to one small glass (up to 125ml) per day, which can count towards their 5-a-day.
Children under two years should not have sweetened drinks. From one year, unsweetened fruit juice should be diluted:
- 1–2 years: 1 part juice to 10 parts water
- Over 2 years: dilute 50% with water
What about caffeine and hydration?
Caffeine has a mild diuretic effect, which means it may cause you to pass urine more frequently, but tea and coffee still contribute to overall fluid intake.
- Adults: safe limit is 400mg caffeine/day
- Pregnancy: limit your intake to 200mg caffeine/day (around 2 cups of coffee)
-
Tea and coffee are not recommended for children as caffeine can interfere with iron absorption and affect sleep
Common drink measures
- Medium glass: 200ml
- Cup: 200ml
- Mug: 250ml
- Can of fizzy drink: 330ml
Special considerations
Children
Children, especially younger ones, may not recognise dehydration.
- Encourage regular drinking throughout the day
- Offer water as their main drink
- Encourage drinking at school where access may be limited
- Good hydration may support attention and memory
Do older adults need more hydration?
Older adults are at higher risk of dehydration and may need reminders to drink regularly.
Do active people need more hydration?
Exercise increases fluid losses through sweat. Water is suitable for most activities. If you are undertaking prolonged or intense exercise, you may benefit from specialist sports drinks.
Top tips
- Drink little and often
- Keep a bottle or jug of water nearby
- Choose unsweetened drinks most of the time
- Encourage children and older adults to drink regularly
- Increase fluids in hot weather or when you are more active
- Drink more when you are unwell, especially with a fever, vomiting or runny poo
- Check your urine colour - aim for a pale straw colour
- Remember that fruit and vegetables also contribute to hydration
Source(s)
- British Heart Foundation. Dehydration: signs, causes, and tips to drink more water [Internet]. London: British Heart Foundation; 1 Feb 2024 [cited 2026 Feb 22]. Available from: https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/signs-of-dehydration
- EFSA. Scientific Opinion on Dietary Reference Values for water. EFSA J. 2010;8(3):2–3. Available from: https://doi.org/10.2903/j.efsa.2010.1459
- NHS inform. Hydration [Internet]. Scotland: NHS inform; c2026 [cited 2026 Feb 22]. Available from: https://www.nhsinform.scot/campaigns/hydration/
- Popkin BM, D’Anci KE, Rosenberg IH. Water, hydration, and health. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan– [updated 2023 Jul 17; cited 2026 Feb 24]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555956/
- Daley SF, Avva U. Pediatric dehydration. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan– [updated 2024 Jun 8; cited 2026 Feb 22]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK436022/
- Li S, Xiao X, Zhang X. Hydration Status in Older Adults: Current Knowledge and Future Challenges. Nutrients. 2023;15(11):2609. Available at: https://doi.org/10.3390/nu15112609
- Edmonds CJ, Foglia E, Booth P, Fu CHY, Gardner M, Dehydration in older people: A systematic review of the effects of dehydration on health outcomes, healthcare costs and cognitive performance. Arch Gerontol Geriatr. 2021;95:104380. Available from: https://doi.org/10.1016/j.archger.2021.104380
- Judge LW, Bellar DM, Popp JK, Craig BW, Schoeff MA, Hoover DL, Fox B, Kistler BM, Al-Nawaiseh AM. Hydration to Maximize Performance and Recovery: Knowledge, Attitudes, and Behaviors Among Collegiate Track and Field Throwers. J Hum Kinet. 2021;79:111-122. Available from: https://doi.org/10.2478/hukin-2021-0065