Can you explain hyponatremia?

Low Sodium: Hyponatremia means that a blood test revealed a low value for sodium. This can be from excess water or less likely insufficient sodium. It can be a very serious problem, you must see your doctor to evaluate and correct this condition.

Low Sodium in Blood: Although the term hyponatremia means "low sodium in blood", it is caused by abnormal handling of water by the kidneys. Reabsorption of water in the kidneys rely on a hormone called ADH (vasopressin) produced in the brain and there are instances where a high concentration is secreted either appropriately (e.g. severe volume contraction) or inapproprately (e.g. medication causing SIADH (vasopressin)).