How Much Water Do I Need?

Picture of Sarah Chan, PA-C, in a lab coat

Author: Sarah Chan, PA-C

Our bodies need water to do all the things needed to keep us alive and healthy. The typical adult is made up of more than half water, but your individual water needs depend on factors including your health, how active you are and where you live. No single formula fits everyone, but knowing your body’s needs for fluids will help you estimate how much water to drink daily. 

Every cell, organ and tissue in your body needs water to work properly. Lack of water can lead to dehydration — a condition that occurs when you don’t have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.

So how much fluid does the average, healthy adult living in a temperate climate need? The U.S. National Academies of Sciences, Engineering, and Medicine determined that an adequate daily fluid intake is:

  • About 15.5 cups (3.7 liters) of fluids a day for men
  • About 11.5 cups (2.7 liters) of fluids a day for women

These recommendations cover fluids from water, other beverages and food. About 20% of daily fluid intake usually comes from food and the rest from drinks. Most healthy people can stay hydrated by drinking water and other fluids whenever they feel thirsty. For some people, fewer than eight glasses a day might be enough. But other people might need more.

You might need to modify your total fluid intake based on several factors:

  • Exercise: If you do any activity that makes you sweat, you need to drink extra water to cover the fluid loss. It’s important to drink water before, during and after a workout.
  • Environment: Hot or humid weather can make you sweat and requires additional fluid. Dehydration also can occur at higher altitudes.
  • Overall health: Your body loses fluids when you have a fever, vomiting or diarrhea. Drink more water or follow a doctor’s recommendation to drink oral rehydration solutions. Other conditions that might require increased fluid intake include bladder infections and urinary tract stones.
  • Pregnancy, monthly period and breast-feeding: If you are pregnant or breast-feeding, you may need additional fluids to stay hydrated.

Some patients ask if water is the only mode for staying hydrated and the answer is no. You don’t need to solely rely on water to stay hydrated. For example, many fruits and vegetables, such as watermelon and spinach, are almost 100% water by weight. 

Benefits of drinking water throughout the day:

  1. Heart health: When you don’t drink enough water, your serum sodium levels increase, which in turn, causes the body to try and conserve water – a process known to contribute to heart failure.
  2. Brain health: Your brain consists of about 73% water and when you don’t have enough in your body, it can slow your ability to focus.
  3. Kidney health: Water helps the kidneys remove waste from the blood.
  4. Join health: Joint cartilage is made up of about 80% water, staying well-hydrated can help cushion and lubricate your joints. 
  5. Metabolism: Drinking enough water can help increase your metabolism by as much as 30%.
  6. Energy: When we’re not sufficiently hydrated, it hampers the flow of nutrients into our cells and clogs waste from flushing out.
  7. Regulates your body temperature.
  8. Immune health: Constantly failing to get enough fluids into your body may depress the immune system and make it harder to fight off illnesses.

You know you’re hydrated if your urine is colorless or light yellow and you rarely feel thirsty. Drinking too much water is rarely a problem for healthy, well-nourished adults. Athletes occasionally may drink too much water in an attempt to prevent dehydration during long or intense exercise. When you drink too much water, your kidneys can’t get rid of the excess water. The sodium content of your blood becomes diluted. This is called hyponatremia and it can be life-threatening.

The information provided is for general interest only and should not be misconstrued as a diagnosis, prognosis, or treatment recommendation. This information does not in any way constitute the practice of medicine, or any other health care profession. Readers are directed to consult their health care provider regarding their specific health situation. Marque Medical is not liable for any action taken by a reader based upon this information.

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