“Hypernatremia is when there’s too much sodium and not enough water in your blood. Sodium is one of the electrolytes in your body, found mostly in your blood. It’s important for many body functions. However, when there’s too much, the imbalance can cause serious problems.

Doctors define hypernatremia as a sodium level of over 145 milliequivalents per liter of blood — a normal level is between 136 and 145 milliequivalents per liter.

It’s most likely to happen in babies or people who are older. Certain health conditions can make hypernatremia more likely. But it’s often a symptom of dehydration — if you don’t have enough water, your blood sodium levels can get too high.”

Web M.D. (Hypernatremia: Danger of Too Much Sodium in Your Blood)