The causes of low sodium levels in the blood include certain medications, kidney, heart or liver problems, and chronic and severe vomiting or diarrhea, explains Mayo Clinic. When sodium levels drop slowly, the condition is called chronic hyponatremia and patients may experience nausea, vomiting, headache and confusion.
Other symptoms include loss of energy and appetite, restlessness, muscle weakness, muscles spasms, coma and seizures, according to Mayo Clinic. Acute hyponatremia is caused by a rapid drop in sodium levels and is more dangerous because it can result in rapid brain swelling, coma and death.
Certain cases of hyponatremia are caused by the dilution of sodium in the body from excess water retention, or an increase in water intake, explains The Merck Manual Professional Edition. A condition that causes this is syndrome of inappropriate anti-diuretic hormone, in which the body produces too much anti-diuretic hormone and causes the kidneys to retain water instead of excreting it in urine. When this occurs, the excess water dilutes the sodium in the blood.
A similar phenomenon happens in patients who drink too much water and is common in athletes who run marathons or participate in endurance exercises, notes Mayo Clinic. They replace lost sweat with regular water and dilute their blood sodium. Other causes of hyponatremia include dehydration, Addison’s disease, low thyroid hormone, and Ecstasy use.