You've probably heard "eight glasses a day". It's a handy reminder, but it isn't a hard rule. How much water you need depends on your size, how active you are, the weather, and what else you eat and drink.
For a rough starting point, the European Food Safety Authority suggests about 2 litres of water a day for most women and about 2.5 litres for most men. That counts water from everything, including food, which usually covers around a fifth of it. So the drinking part is often a little less than those numbers.
Your body is good at telling you, too. Drink when you're thirsty, and glance at your wee: pale straw colour usually means you're doing fine, while dark yellow is a nudge to have a glass. You'll likely need more on hot days, during exercise, or if you're unwell.
Fasting changes things a little. When you skip meals, you also skip the water that food brings, so it's worth sipping a bit more through the fast. Water, fizzy water, plain tea and black coffee all count towards your total.
On longer fasts of a day or more, some people also take electrolytes such as sodium, potassium and magnesium, because those usually come from food. Please talk to your doctor before you do, especially if you have heart or kidney problems or take blood pressure medication. And don't force down huge amounts of water: more than your body needs, very quickly, can dilute the salt in your blood.
In Step Step, pick a daily goal that suits you and tap to log each drink. Water from other apps that save to Apple Health counts too.
How much water should you drink a day?
The European Food Safety Authority gives about 2 litres of total water a day for most women and about 2.5 litres for most men, including water from food. In practice, that often means roughly 1.5 to 2 litres from drinks, though individuals vary. Children, older adults and pregnant or breastfeeding women have different guidelines.
These are averages, not targets to hit exactly. Your own need moves up and down with the weather, your activity, your body size and what you eat. A day of salty food and a long walk in the heat will ask for more than a quiet day indoors.
How can you tell if you are drinking enough?
Thirst is a reliable signal for most healthy adults. Drink when you feel thirsty, and a little extra with meals or exercise. Urine that is pale straw coloured through the day is a good sign. Dark yellow, or going many hours without needing the toilet, suggests you could drink more.
Be aware that some foods and supplements, such as B vitamins or beetroot, change urine colour, so use it as one clue among several. Headaches, dry lips and tiredness can also be signs of low fluid, though they have many other causes.
Do tea, coffee and other drinks count?
Yes. Tea, coffee, milk, juice and soups all contribute to your fluid intake. Moderate caffeine has only a mild effect on urine output, and the water in the drink more than makes up for it. Plain water is still a good default because it has no calories or sugar, but variety is fine.
Sugary drinks and alcohol are another matter. They add energy, and alcohol makes you pass more urine, so they are not a good main source of fluid.
A simple habit is to keep a bottle or glass in sight. Most people drink more when water is within reach. Flavouring plain water with lemon, cucumber or mint is fine if it helps you drink more, and the Water Intake Calculator can give you a personal starting figure based on your size and activity.
How should you drink water while fasting?
Spread drinks through the day instead of waiting until you feel parched. A glass on waking, one mid-morning and one in the afternoon is an easy rhythm. Water, fizzy water, plain tea and black coffee all keep you topped up without breaking most people's idea of a fast.
If you fast for longer than a day, thirst can feel different and you may not notice that you are getting dry. Keep a bottle nearby, sip regularly, and notice headaches, dizziness or a racing heart, which can be signs that you need fluid, salt or a proper meal. Break the fast and seek advice if they do not ease.
Take extra care if you take medicines for blood pressure or diabetes, have kidney or heart problems, are pregnant, or have a history of eating disorders. Fasting with these needs advice from your doctor first. Step Step's Water History shows your logged drinks over time.
Common questions
Is 2 litres of water a day enough?
For many adults, 2 litres of total fluid is a reasonable guide, and part of that comes from food. Your own need depends on heat, activity and health, so use thirst and urine colour alongside the number.
Can you drink too much water?
Yes, though it is uncommon. Drinking very large amounts quickly can dilute the sodium in your blood, which can be dangerous. Sip steadily and stop if you feel sick or confused.
Does water break a fast?
No. Plain water has no calories and does not break a fast. Fizzy water, plain tea and black coffee are also commonly accepted.
How much water should you drink during a fast?
Aim to drink to thirst and a little more, as you are not getting water from food. If you feel dizzy, faint or unwell, stop fasting and seek medical advice.
Updated October 25, 2026
This is general information, not medical advice. Check with your doctor before you start fasting, especially if you have a health condition, are pregnant or take medication.
