What Causes Low Sodium in the Blood?

Low sodium in the blood, or hyponatremia, has several possible causes, including certain medications, syndrome of inappropriate anti-diuretic hormone, hormonal changes and heart, kidney or liver conditions. Other sources of low sodium are overconsumption of water, dehydration, use of ecstasy and chronic vomiting or diarrhea, states Mayo Clinic.

Drugs that cause users to sweat or urinate more frequently sometimes lead to hyponatremia, according to Mayo Clinic. These include diuretics — also known as water pills — antidepressants and pain medications.

Syndrome of inappropriate anti-diuretic hormone most often occurs in people with heart failure or brain injuries, and the body produces too much antidiuretic hormone, the University of Rochester Medical Center explains.

If thyroid or adrenal glands do not make sufficient hormones, hyponatremia sometimes develops, states Mayo Clinic. Certain diseases, such as congestive heart failure, influence blood sodium levels. In addition, hyponatremia occurs when too much liquid is consumed or too much body fluid is lost.

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.