Sodium levels in the blood normally range from 135 to 145 milliequivalents per liter, or mEq/L, according to the National Library of Medicine. Ranges may be slightly different between laboratories.
Higher than normal sodium concentrations can be caused by diabetes insipidus, fluid loss or eating too much salt or sodium bicarbonate. Low levels of sodium can be caused by high water levels in the body, hormone problems or the buildup of waste material. Certain medicines, adrenal gland problems and fluid loss can cause too low or too high levels of sodium. A simple blood test is used to measure the sodium content in blood, according to the National Library of Medicine.