There are no exact rules for how much water to drink while exercising, because everyone is different. You need to consider factors including your sweat rate, the heat and humidity in your environment, and how long and hard you are exercising.
Dehydration happens when you lose more fluid than you drink. When your body doesn’t have enough water, it can’t work properly. Dehydration can range from mild to severe.
Symptoms of dehydration can include the following:
Dizziness or lightheaded feeling.
Nausea or vomiting.
Muscle cramps.
Dry mouth.
Lack of sweating.
Hard, fast heartbeat.
Symptoms of severe dehydration can include mental confusion, weakness, and loss of consciousness. You should get emergency medical attention immediately if you have any of these symptoms.
