Not sure about how much water exactly you should be drinking while out on your daily run or at a race? Since water constitutes of up to 70% of our bodies, it is no surprise that it is vital for our lives, functioning and wellbeing. Still, many people fail to drink sufficient quantities of water during the day. Others though may be taking in too much water. So, how do you find the balance and drink as much water necessary to keep you well hydrated and performing at your best when running?

Here are some tips to follow, to ensure that you are consuming the right quantity of water during the day and when running:

1. Remember to stay hydrated all day long

Water is essential not only when you are running or exercising, but for normal everyday functioning as well. The well-known rule of the thumb is to drink 8 glasses of water throughout the day. But you should start and end your day with a glass of water, and in the meantime make sure you intake as much water as necessary to never feel thirsty or dehydrated.

When you are preparing for a race, you should prepare your body for an increased intake of water. This means you should start drinking more water during your pre-race training period, so that you are able to consume the increased volume of water during the actual race. Staying hydrated during a race is essential for your running performance and for your health.

2. Drink some water every time you are thirsty during a run

Stick to the general rule of drinking about 4 to 6 ounces of water every 20 minutes during your run[1]. The quantity and the intensity of water intake will increase as the distance and your pace increase. Also, when it is hotter, you are more likely to sweat more so you will need more liquids to replace the lost minerals and help maintain a healthy electrolyte balance. If you are running for over 90 minutes, you should add electrolyte drinks for better hydration and to ensure that the sodium, potassium and other essential minerals and substances you are losing through perspiration during the run are replenished in a proper and timely manner without risking getting over-hydrated.

According to International Marathon Medical Directors Association, the optimal quantity of water which needs to be consumed during a marathon is 13.5 to 27 ounces (400 – 800 ml) per hour, so keep this measure in mind when preparing for or running a marathon. Here is what they say:

GUIDELINE # 5: Runners should aim to drink ad libitum between 400 – 800 ml per hour, with
the higher rates for the faster, heavier runners competing in warm environmental conditions
and the lower rates for the slower runners/walkers completing marathon races in cooler
environmental conditions.[2]

– IMMDA advisory statement on guidelines for fluid replacement during marathon

3. Prepare your body for the race by fortifying it with water and electrolyte sports drinks

Drink about 16 ounces of water and electrolyte-based sports drinks an hour or two before a race to prepare your body properly. Take in 5 to 12 ounces per 15-20 minutes during the run. If you are running for less than 90 minutes, drinking only water should be sufficient to keep you hydrated.

4. Don’t overdo it!

If you feel a sloshing feeling in your stomach, this means that it is full and you should stop the intake of water for some time. The amount of water needed to fill your stomach depends on your gender, size, age, metabolism and other factors, so watch yourself carefully as you are running. Another symptom of getting too much water is if you start feeling nauseous or crampy during the run. Stop the intake of liquids for about 15 minutes if you feel the signs that you have had too much.

Bear in mind that the condition known as Hyponatremia[3] or “water intoxication” can be very dangerous and even fatal. This condition most commonly can occur during long runs in hot weather conditions, when the body starts losing more sodium, which cannot be replaced by the plain water consumed. This can cause a dangerous electrolyte imbalance in your body, which can lead to serious consequences, including: seizures, coma and in extreme cases – death. Some early warning symptoms include: disorientation, vomiting, muscle weakness and confusion. Women and endurance runners are more likely to be affected by this condition. In order to prevent it, make sure you eat sufficient amounts of salt in your daily diet and especially prior to a long distance race, and also make sure you drink some electrolyte sport drinks rather than just plain water during your long-distance run.


Remember that our bodies are different, and the way we use up and sweat out the water varies. Make sure you watch your body and find the perfect balance for yourself to allow you to stay hydrated during your run or race. Overhydrating can lead to unfavorable side effects too, so make sure you are not overdoing it, so stick to the rule that you must replace the amount of water lost during the run and you should be OK!


1. Men’s Health Total Fitness Guide 2006, by Deanna Portz
2. Advisory statement on guidelines for fluid replacement during marathon running  by International Marathon Medical Directors Association
3. Hyponatremia: A practical approach by Dr. Manisha Sahay, Rakesh Sahay, published on National Center for Biotechnology Information, U.S. National Library of Medicine