Hypernatremia is an increase in ____________ sodium levels above normal.

Hypernatremia refers to a condition where there is an elevated level of sodium in the blood, specifically in the plasma. Plasma is the liquid component of blood that carries red and white blood cells, nutrients, hormones, and waste products. When determining the sodium levels in the body, measurements are typically expressed in terms of plasma sodium concentration. An increase in plasma sodium indicates that there is a higher-than-normal amount of sodium relative to the amount of water in the body, which can lead to various physiological problems such as dehydration of cells and disturbances in fluid balance. Therefore, the correct answer highlights the importance of measuring sodium levels within plasma to accurately assess a person's electrolyte status and health condition.