The causes of a low sodium level include dehydration, kidney problems, severe vomiting or diarrhea, hormonal changes and the use of certain medications, states Mayo Clinic. Low sodium levels are also caused by heart problems, drinking excessive amounts of water, liver problems and the use of Ecstasy, an amphetamine.
The medical term for a low sodium level is hyponatremia, reports MedlinePlus. This condition interferes with the normal balance of sodium and water in the body. In hypovolemic hyponatremia, a person loses both water and sodium, but the sodium loss exceeds the water loss. A person with hypervolemic hyponatremia gains both sodium and water, but the increase in water content is greater than the increase in sodium content. Euvolemic hyponatremia occurs when there is an increase in total body water without an accompanying increase in sodium.
Without the right amount of sodium, the nerves and muscles do not work properly, states MedlinePlus. Sodium is also used to maintain normal blood pressure. A person with hyponatremia has symptoms such as fatigue, muscle spasms, convulsions, muscle weakness and vomiting. Severe hyponatremia can cause the brain to swell, making it a dangerous condition. Treatments for hyponatremia include intravenous fluid therapy and restricted water consumption. If hyponatremia develops as the result of cancer, treating the cancer with surgery, chemotherapy or radiation therapy can correct the sodium imbalance.