Hyponatremia is a serious medical condition in which blood sodium (NA+) levels are below 130 mmol·L−1. This can occur when an individual drinks more fluid than necessary or large amounts of Na+ are lost through sweat. Symptoms include disorientation, altered mental status, coma, headache, vomiting, bloating, lethargy, and swelling of the extremities. These symptoms may develop during exercise or several hours after exercise is discontinued. Reducing the risk of hyponatremia includes the ingestion of Na+ containing fluids and the avoidance of overdrinking. Coaches and athletes should be aware of the signs and symptoms of hyponatremia, how to reduce the risk of hyponatremia, and when to contact medical professionals.