Reviewed by Rishi Desai, MD, MPH
Hypernatremia is an elevated sodium level in the blood. Normal serum sodium levels are between approximately 135 and 145 mEq/liter (135 - 145 mmol/L). Hypernatremia is generally not caused by an excess of sodium, but rather by a relative deficit of free water in the body. For this reason, hypernatremia often coincides with dehydration.