Hyponatremia is defined as a serum sodium of less than 135 Meq per litre and occurs in upto 22 % of hospitalised patients. The causes of hyponatremia may be understood based on the pre-existing volume status of the patient which may either be hypovolemic, euvolemic or hypervolemic hyponatremia. This presentation discusses in detail, the causes of these underlying conditions. Also mentioned are the clinical features and management options and therapeutic sodium targets in patients with hyponatremia. Drugs such as demeclocycline and vaptans (Tolvaptan, Conivaptan) are also mentioned as management options which may be used on a case to case basis. Finally, the all important targets of sodium correction over 24 hours are also mentioned, along with a practical formula for calculation of sodium deficit which is explained with an example.