You have probably heard the advice to drink eight glasses of water a day. But is that really the right amount for everyone? This guide explains how much water you should drink a day, what affects your needs and how to tell if you are drinking enough.
This article is general information, not medical advice. If you have a health condition, ask your doctor how much fluid is right for you.
How Much Water Should You Drink a Day?
There is no single number that fits everyone. A commonly cited guide comes from the US National Academies of Sciences, Engineering, and Medicine. It suggests an adequate total water intake of about:
- 3.7 liters (about 15.5 cups) a day for men
- 2.7 liters (about 11.5 cups) a day for women
These amounts cover all fluids and the water in food. About 20 percent of daily water usually comes from food, such as fruit, vegetables and soup. The rest comes from drinks.
So you do not need to drink that full amount as plain water alone.
Is the “8 Glasses a Day” Rule True?
The eight-glasses rule (about 2 liters) is an easy rule of thumb, but it is not a scientific law. Some people need less, and many need more, depending on their body and lifestyle.
What Changes How Much Water You Need?
- Exercise: you lose water through sweat, so you need more.
- Hot or humid weather: sweating increases.
- High altitude: you may lose more fluid.
- Illness: fever, vomiting and diarrhea cause water loss.
- Pregnancy and breastfeeding: fluid needs are higher.
- Body size and diet: bigger bodies and salty or high-protein diets may need more.
- Some medicines and health conditions: some conditions may need more fluid, and others, such as certain heart or kidney conditions, may require limits.
How to Tell if You Are Drinking Enough
Check Your Urine Color
Pale yellow urine usually means you are well hydrated. Dark yellow or amber can be a sign that you need more fluid.
Notice Your Thirst
For most healthy adults, thirst is a reliable signal. Drink when you feel thirsty.
Signs of Dehydration
Possible signs include a dry mouth, headache, dizziness, tiredness and urinating less often. Severe dehydration is serious, so seek medical help if you feel very unwell.
Do Other Drinks Count?
Yes. Tea, coffee, milk, juice and sparkling water all contribute to your fluid intake. Water is usually the healthiest choice, because it has no sugar and no calories.
Sugary drinks add calories, so it is wise to limit them. Alcohol can increase fluid loss, so it is not a good way to hydrate.
Simple Ways to Drink More Water
- Start your day with a glass of water.
- Carry a bottle that you like and refill it.
- Drink with meals, and have a glass between meals.
- Add flavor with lemon, cucumber or mint if plain water feels boring.
- Eat water-rich foods, such as oranges, cucumber and watermelon.
- Use reminders if you tend to forget.
Can You Drink Too Much Water?
Yes, although it is rare. Drinking very large amounts of water in a short time can lower the level of sodium in your blood, a condition called hyponatremia. It is most often a concern for endurance athletes and people with certain medical conditions.
For most healthy people, drinking to thirst is safe and enough.
Learn More
For a clear overview from a major medical center, you can read the Mayo Clinic guide to water intake.
Frequently Asked Questions
How many liters of water should I drink a day?
A common guide is about 3.7 liters of total water for men and 2.7 liters for women, including drinks and food. Your own needs can be higher or lower.
Is 2 liters of water a day enough?
For many people, drinking about 2 liters of fluid, along with water from food, is a reasonable amount. Needs rise with heat, exercise and illness.
Does coffee dehydrate you?
Moderate coffee intake generally counts toward your daily fluid. Very high caffeine intake may not be healthy for other reasons.
What is the best time to drink water?
Any time is fine. Spreading it through the day, and drinking more around exercise, works well for most people.
Should I drink more water if I exercise?
Yes. Drink before, during and after exercise, especially in hot weather.
Conclusion
How much water you should drink a day depends on your body, your activity and the weather. A general guide is about 2.7 liters of total water for women and 3.7 liters for men, including drinks and food.
Listen to your thirst, check your urine color, and talk to a doctor if you have a medical condition that affects fluids.