In non-athletes, it usually only happens in people with problems that cause the kidneys to retain too much water or during dangerous activities such as hazing rituals and the use of certain illegal drugs.
It is more common in athletes, such as long distance runners and triathletes because kidney function is reduced during intense exercise. When athletes drink too much water and do not replace adequate sodium during a long event, their body can retain too much fluid, resulting in hyponatremia, a dangerous dilution of blood sodium. This can be fatal. Warning signs of hyponatremia include; continued thirst despite fluid intake, nausea, headache, inability to concentrate and confusion. Medical assistance should be sought out, immediately.