Hydration basics

You do not need an app or a formula to drink enough water. A few habits and a little attention to the days that are different will do.

How much is enough?

Needs vary with body size, activity, climate and what you eat, so there is no single number that fits everyone. A practical guide for most healthy adults is to drink regularly through the day, let thirst be a signal rather than something to push through, and aim for pale-yellow urine. Food counts too: fruit, vegetables, soups and yogurt all carry water.

When the day is different

Hot weather, long walks, hard training, air travel and illness all raise how much fluid you lose. On those days, drink before you feel thirsty, and keep going after the activity ends. If you have been sweating heavily for an hour or more, plain water alone can leave you short of the salts you lost with it.

Where electrolytes come in

Sweat carries sodium, and smaller amounts of potassium and magnesium, out of the body. For an ordinary day, a normal diet replaces them without any help. After long, sweaty sessions or a day in the heat, an electrolyte mix in your water replaces what you lost and makes it easier to drink enough. Pick one with a sensible amount of sodium and not much sugar, and read the label so you know what is in a serving.

Easy ways to keep up

• Keep a bottle you like within reach, at your desk, in the car and by the bed.
• Drink a glass of water when you wake up and with each meal; three habits, three glasses.
• If plain water bores you, add citrus, cucumber, mint or a hydration tablet.
• Coffee and tea count toward your fluid intake; alcohol works the other way.
• Carry water on walks and errands in warm weather, not just to the gym.

Signs you are behind

Headache, tiredness, dark urine, dry mouth and feeling lightheaded when you stand up are common early signs. Drink, rest in the shade if it is hot, and ease off until you feel normal. Severe symptoms such as confusion, fainting or an inability to keep fluids down need medical attention.

This guide is general information for healthy adults, not medical advice. People with kidney or heart conditions, and anyone on a fluid- or salt-restricted diet, should follow their healthcare provider’s guidance.