How much water should you drink a day?
There is no one number that fits everyone. A useful rule: drink enough that you rarely feel thirsty and your urine is pale yellow, and spread it across the day.
The numbers people quote
The US National Academies set an adequate daily intake of total water of about 3.7 litres for men and 2.7 litres for women. Total water includes everything: plain water, tea, coffee, milk, juice, and the water inside food. Food usually supplies about 20 percent, so most people need roughly 3 litres of drinks (men) and 2.2 litres (women). Treat these as a starting point, not a target to hit exactly.
What changes how much you need
- Heat and humidity: you lose more through sweat.
- Exercise: drink before, during and after, especially over an hour.
- Pregnancy and breastfeeding: needs go up.
- Illness: fever, vomiting and diarrhoea cause fast fluid loss.
- Altitude and dry air-conditioned rooms: both increase loss.
- Age: older adults feel thirst less, so a schedule helps.
A simple way to check
Look at your urine colour. Pale straw yellow usually means you are well hydrated. Dark yellow suggests you need more. Headache, tiredness and dry lips are other common signs of being short on fluid.
An easy daily pattern
- One glass when you wake up.
- One glass with each meal.
- One glass mid-morning and mid-afternoon.
- A glass after any exercise.
- Taper off an hour or two before bed so sleep is not broken.
That is about eight glasses without thinking about it. If you keep forgetting, a timed reminder works better than willpower. See 9 ways to remember to drink water.
Can you drink too much?
It is uncommon, but drinking very large amounts in a short time can dilute blood sodium. Sip steadily instead of forcing litres at once.
When to follow your doctor instead
If you have kidney, heart or liver conditions, take diuretics, or have been told to limit fluids, follow your doctor's advice rather than general numbers. This guide is general information, not medical advice.
Never forget again
TwoToTango pops up a short video of someone you love to remind you to drink water. Free for Android, Windows and Mac.