Humans have an unquenchable thirst for water. It's the most important nutrient for us on the planet, and ideally, we should be drinking water every day. For many, it's a challenge to keep up with this near-constant need for water.

Dehydration is one of the most common preventable medical conditions in the world, and it affects millions in the United States. Yet for something so common, most of us are unaware of its dangers Dehydration Causes Fatigue.

People who are even mildly dehydrated were much more likely to feel fatigued during moderate exercise and even when sedentary. Unsurprisingly, fatigue is a common dehydration symptom, and it's said to be the No. 1 cause of midday fatigue. Thirst Means You're Dehydrated. Dehydration triggers the body's thirst response. So when you feel thirsty, dehydration is already setting in. In many experiments, just 1 to 2 percent dehydration has been shown to trigger thirst. This level of dehydration can happen quickly, especially following intense exercise or when battling viruses.