Three Important Tips for Proper Hydration

One important question for runners is how much should we drink.  We understand that we lose a lot of fluid while running and fluid replacement is a must.  But too much or too little is very risky and pose a lot of danger to our health.

In fact, drinking too much can be a much worse condition than drinking too little.  According to a study published in The New England Journal of Medicine last April 2004, about 13 percent of runners in the 2002 Boston Marathon might have suffered from hyponatremia, a dangerous condition caused by drinking too much fluid.

So much should we drink?  What should we drink?  Should I drink more if I run fast or if I run slow?

1.  Favor sports drink over water.

According to a study approved by the International Marathon Medical Directors Association (IMMDA) in 2006, “if your event or workout is longer than 30 minutes you should be drinking a sports drink. The added carbohydrate and electrolytes speed absorption of fluids and have the added benefit of energy fuel and electrolytes. There is actually decreased benefit to watering down or diluting sports drinks or alternating sports drinks with water.”

But don’t expect sports drinks to prevent hyponatremia. They won’t.

The International Marathon Medical Directors Association (IMMDA) was formed as the Consulting Medical Committee of the Association of International Marathons (AIMS).

2.  Drink according to thirst.

While there are calculation guidelines on how to determine the amount ofwater intake based on your weight, the best advice by medical experts is to drink ad libitum, or to drink according to one’s thrist.

Each persons need is unique and thrist is the best indicator if you needto hydrate or not.  I find this as a safer approach compared to calculation guidelines.  Fluid calculation guidelines can vary based on sweat rate, location, climate, humidity and other factors.

When drinking, take fluids in small quantities rather than taking in big gulps in every station.

3.  Avoid weight loss or weight gain during the race.

Since runners take in mostly fluids during a race, any weight gain is a possible sign of overhydration.  At the same time, a weight loss of morethan 2% is a possible sign of dehydration.

IMMDA recommend this table as an approximation of fluid replacement.  But remember that thrist is still the best method recommended by experts.

Finish Time

Race Pace

Fluid Intake


Fluid Intake Total
< 4 hours 10-12 oz / 20minutes 3.5-4.0 liters
< 8 minutes/mile 30-36 oz / hour
1000-1250 ml/hour
4-5 hours 8 oz / 20 minutes 3.0-3.5 liters
9-10 minutes/mile 24 oz / hour
750 ml / hour
> 5 hours 4-6 oz / 20 minutes 2.5- 3.0 liters
> 10 minutes/mile 18 oz / hour
500-600 ml/hour

What I find interesting in this table is that the slower you are, the lesser your fluid intake should be.  Slower race pace = Slower drinking rate.  Thus, a safe range is to drink fluids between 400 – 800 ml per hour based on Dr. Tim Noakes study in 2002.

Remember that the table above is just an approximation.  Actual fluid intake will vary depending on the runner’s sweat rate and other environmental factors.

If you are inrested to read more of the 2002 study entitled IMMDA Advisory Statement on Guidelines for Fluid Replacement during Marathon Running by Dr. Tim Noakes, you can download it here.

Run safe everyone.


Training for a race? Check out our list of training plans below.
5K Training 10K Training 21K Training 42K Training


Sign up to our newsletter and get the latest updates right to your inbox everyday. Simply add you email address below.

Filed Under: Running for Beginners, Training


Hey Running Buddy! We Love to Hear a Comment From You. :D