Hydration for Athletes

I recently received the following question from a reader:  

Q: I don’t drink any soda or anything but water ( and some Gatorade or vitamin water when I am playing). Can I be drinking too much water?  I drink about 136 oz of water a day. (Like 8 bottles).

A:  Yes, it is possible to drink too much fluid which can lead to a condition called hyponatraemia (low levels of sodium in the blood).  This only occurs in extreme cases, and is most often seen in prolonged exercise (>2 hours) when large volumes of low-sodium drinks are consumed and very little sweat is lost.  This has mostly been seen in long distance runs, like marathons, and is more common with women.  Drinking beverages which contain sodium, like a sports drink, can lower the risk of hyponatremia.

Dehydration is much more common among athletes.  On average, a person needs a minimum of 4 cups (32 oz) of fluid for every 1,000 calories.  Any sweat losses with exercise would increase your fluid needs beyond that.  There is not a “one size fits all” fluid replacement plan because athletes vary greatly with the amount of sweat they lose with activities.  Fluid losses are affected by several factors:

  • Genetics and build- some people naturally sweat more than others, and larger athletes sweat more than smaller one.
  • Fitness levels- as your fitness improves, you will start to sweat sooner when you exercise and in larger volumes
  • Type of exercise- more intense exercise will increase sweat losses
  • Temperature- Hot, humid weather causes people to sweat more
  • Medications- certain medications change fluid needs.

People often lose around 2-4 pounds (4-8 cups or 32-64 oz) per hour with moderate exercise in a mild environment.  The best way to determine fluid losses is to weigh yourself before and after you exercise and then factor in the weight of any drinks consumed.  An example: 

Pre-exercise weight = 150 pounds

Post-exercise weight= 145 pounds

Volume of fluid consumed during exercise =16 oz (1 pound)

Exercise duration = 2 hours


Fluid deficit = 150 lb – 145 lb = 5 lb

Total sweat loss= 5 lb + 1 lb consumed = 6 lb

Sweat rate = 6 lb/ 2 hours = 3 lb per hour

You want to drink 2 cups of water for each pound lost.  If you gain weight during exercise, then that will show you that you are drinking more than you need (that is when you can run the risk of over hydration).  If that seems like too much work, you should just monitor the color of your urine.  It should always be a light yellow and relatively odorless…if it gets darker colored than straw, you should be drinking more. 

A good guideline for hydrating yourself with exercise is as follows:



2-3 hours before exercise 16-24 oz (2-3 cups)
30 minutes before exercise 5-10 oz (~½-1 cup)
During exercise 5-10 oz (~½-1 cup) every 15 minutes
After exercise > 20 oz (2½ cups) for every pound lost during exercise

I would recommend sports drinks that replace sodium and electrolytes over vitamin water (although that is not the worst choice).  Some good choices are:

  • Gatorade
  • PowerAde
  • PB Fluid & Electrolyte Replacement

The 17 cups of water a day that you are currently drinking, may be appropriate if you are sweating a lot with your sport (or if you are doing very physical work at your job that causes you to sweat).  However, it would likely be quite a bit more than you would need on days that you are doing little activity.  I would use the above information to assess your needs.