Exercise-associated hyponatremia, is a fluid-electrolyte disorder caused by a decrease in sodium levels (hyponatremia) during or up to 24 hours after prolonged physical activity.[1] This disorder can develop when marathon runners or endurance event athletes drink more fluid, usually water or sports drinks, than their kidneys can excrete.[2] This excess water can severely dilute the level of sodium in the blood needed for organs, especially the brain, to function properly.[2]