How Much Water Do You Need Per Day?

Water is the most important chemical component in the body. Making up approximately 60% of your body weight, every body system depends on water to function properly. Water carries nutrients to your cells and flushes toxins out of vital organs. When you don’t consume enough water, your body can enter into dehydration, which can drain your energy and make you tired.

How much water do I need a day?

This is a common question that health professionals hear. In general doctors recommend 8 to 9 cups per day, however since every body is different, there are a few ways to figure out the proper amount.

  • 8 x 8 Rule — An easy rule to remember is to “Drink eight 8-ounce glasses of water each day.” This amounts to approximately 1.9 liters, which is equivalent to the average amount of fluid loss for an average healthy adult.
  • Fluid Replacement Approach — The replacement approach factors in the amount of fluid loss per day as a guide to the amount you should consume. The average urine output for a healthy adult is approximately 1.5 liters (6.3 cups) per day. An additional liter is lost through everyday bodily functions including breathing, sweating, and bowel movements. Food usually accounts for 20% of your total fluid intake. Therefore, consuming approximately 2 liters of water, along with a normal healthy diet, will typically replace the fluid lost in a day.
  • Dietary Recommendations — The Institute of Medicine advises that men consume approximately 3 liters ( about 13 cups) of total fluid per day and women consume 2.2 liters (about 9 cups) of total fluid per day.

Regardless of which approach you use, as a general rule, if you drink enough fluid so that you rarely feel thirsty and produce 1.5 liters (6.3 cups) or more of colorless or slightly yellow urine a day, your fluid intake is probably adequate.

Factors that influence water needs

The greatest influence on your personal water intake depends on how active you are. Other important factors include the climate you live in, your health status, and if you’re pregnant or breast-feeding.

  • Exercise – any activity that makes you sweat means you are losing more fluid. You need to drink an extra 1.5 to 2.5 cups of water for short periods of exercise, however intense exercise lasting more than an hour requires more fluid intake. During long sessions of intense exercise, it is best to not only drink water but also consume a sports drink that contains sodium, as this will help replace sodium lost in sweat and reduce the chances of developing hyponatremia, which can be life-threatening. Even after exercise is complete, it is important to continue drinking water.
  • Environment – Hot or humid weather increases the body’s temperature and can make you sweat, thus causing you to lose more fluid. In the wintertime, most indoor areas are kept at a heated temperature which can cause your skin to lose moisture and dry out. Altitudes greater than 8,200 feet may trigger increased urination and more rapid breathing, which uses up more of your fluid reserves. In these situations, be sure to continually drink fluids throughout the day to avoid dehydration.
  • Illnesses or health conditions — If you suffer from illness that causes fever, vomiting or diarrhea, your body loses much more fluid than average. In these cases, you should drink more water to replace the fluid loss. In cases of severe vomiting or diarrhea, contact your doctor for their recommendations to replenish the fluid loss and evaluate and treat the cause of the illness.
  • Pregnancy or breast-feeding. Women who are expecting or breast-feeding need additional fluids to stay hydrated. Large amounts of fluid are used especially when nursing. The Institute of Medicine recommends that pregnant women drink 2.3 liters (about 10 cups) of fluids daily and women who breast-feed consume 3.1 liters (about 13 cups) of fluids a day.

But I’m Not Thirsty!

It’s generally not a good idea to use thirst alone as a guide for when to drink. By the time your body is telling you to become thirsty, you may already be slightly dehydrated. As you get older your body is less able to sense dehydration and send your brain signals of thirst. On the other hand, excessive thirst and increased urination can be signs of a more serious medical condition. Talk to your doctor if you experience either of these situations.

To prevent dehydration and make sure your body has the fluids it needs to function optimally, make water your beverage of choice. Most healthy adults can follow these tips:

  • Drink a glass of water with each meal and between each meal
  • Hydrate before, during and after exercise
  • Substitute sparkling water for alcoholic drinks at social gatherings
  • Substitute soda pop and carbonated beverages for coconut water which is low in carbohydrates, 99% Fat Free, and low in sugars. Coconut water contains organic compounds possessing healthy growth promoting properties

SOL  wants to encourage you to enjoy this summer season to the fullest and keep up your water intake!Right now is the best time to be enjoying the outdoors doing the things you love. When you pack up to head outdoors, be sure not to forget a water bottle or two.

At SOL, we are here to help you maintain your active lifestyle. Call today to make an appointment and we’ll help keep you on track!

About the author

Sports + Orthopedic Leaders Physical Therapy & Performance Training serves the communities of Oakland, Alameda, Berkeley, Walnut Creek, Orinda, San Francisco and beyond. SOLPT’s award winning team of Physical Therapists, Performance Coaches and movement experts has helped thousands reach their rehabilitation and performance goals to move beyond pain. We're committed to helping anyone of any fitness level move effectively and more powerfully for a lifetime. We offer rehabilitation and performance services to all populations, with specialties in Sports Rehabilitation, Active Release Techniques, and Manual Therapy Techniques plus Personal and Small Group Training, Sport Clinics and Wellness Services.

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