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How much water should I drink?

man drinks water from a bottle after completing a race

You may have heard you should drink 8 glasses of water a day. The truth is actually close to that, but depends on who you are, where you live, and how much exercise you get each day.

According to Mayo Clinic, water makes up about 60% of your body weight, and every system in your body depends on it. If you don’t get enough water, you may feel tired and can get dehydrated. That’s because your body keeps losing water through breathing, sweating, and going to the bathroom. You need to keep drinking fluids to replace the water your body uses.

You know you’re drinking enough water if you are usually not thirsty and your urine is clear or light yellow.

These tips from Mayo Clinic staff will help you figure out how much water to drink every day:

  • Most men need about 13 cups of fluids a day and most women need about 9.
  • While water is best, beverages including milk and juice are mostly water – so those count, too. Drinks containing caffeine, alcohol, or lots of sugar – including beer, wine, coffee, tea, and soda – should be limited.
  • Food also contains fluid. A typical diet gives you about 20% (or ⅕) of the fluids you need. Many fruits and vegetables, such as watermelon and zucchini, are mostly water by weight.
  • You need more fluids to replace what you lose through sweating. Drink an extra cup or 2 of water after exercising, in hot or humid weather, or if you have a fever.
  • You may also need more fluids in dry conditions such as inside with the heat on, or at high altitudes.
  • Women who are pregnant need an extra cup of fluid a day and women who are breast-feeding need about 4 extra cups.
  • Bottom line: Drink a glass of water with each meal, between each meal, and before, during, and after exercising.

Some warnings

  • It is possible to drink too much water and overwhelm your kidneys, though this happens only very rarely, and hardly ever in healthy adults who eat a typical diet.
  • Some people with health conditions including heart failure and some types of kidney, liver, and adrenal diseases may be told by their doctor to limit how much fluid they drink.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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