What are the causes of low sodium levels in the blood?

Dehydration, Addison's disease, an excessive amount of vasopressin and the use of certain medications are all causes of low sodium levels, according to MedlinePlus. A normal sodium level ranges from 135 to 145 milliequivalents per liter.

Low sodium levels can be caused by diarrhea, vomiting and an increase in the total water content of the body, states MedlinePlus. People with liver cirrhosis, heart failure and some types of kidney diseases sometimes experience increases in their total water content. In some people, a low sodium level is caused by the inappropriate secretion of antidiuretic hormone. Ketonuria, or a build-up of waste products generated by fat metabolism, also causes low sodium levels.