How Much Fluid Should I Drink While Running?

The answer to this question is different for every person because we all have different sweat rates. It also depends on weather conditions and how far or how long you will be running.

If you are running in temperatures under 70 degrees, you should be able to run an hour without having to take in fluids. So most people should be able to run a 5k or 10k race without having to carry or stop for water. However, if you are exceptionally heavy, or the humidity is really high, this may not be true.

Studies have shown that performance starts to be significantly affected after one loses more than 2% of their body weight from fluid loss through sweat. So how do you know how much weight you lose while running? You must do a sweat rate test. It is best to do this in several types of weather conditions and depending on the conditions during your run or race you will know approximately how much to drink.

I recommend a one-hour test. The best and most accurate way to do this is to weigh yourself, in just your running shorts, before you run. It is best to use a scale with 0.1 to 0.2 increments for accuracy. Make sure you drink any fluids and go to the bathroom first. After you have weighed yourself do a one-hour run without drinking anything during the run. Immediately after the run weigh yourself again in just your running shorts. I weigh 162 pounds. At 60 degrees and 50% humidity I will lose about 2 lbs in one hour. Bump the temperature up to 75% and I will lose 3 lbs or more an hour. So how does this translate into how much you should be drinking?