Dehydration is a medical condition in which a body contains insufficient amounts of water for normal functioning. Dehydration can be very dangerous for people, and there are many different causes for dehydration. Prolonged activity or work, especially in a hot or humid environment, is a major cause for dehydration. This is an obvious risk for athletes. A long sports contest can result in major dehydration if athletes do not take the proper precautions to remain hydrated. Other causes for dehydration include vomiting, shock, diarrhea, and blood loss.