What characterizes hyperkalemia?

Hyperkalemia is characterized by an excess of potassium in the bloodstream, which is defined by having a serum potassium level greater than 5.0 mEq/L. Potassium is a crucial electrolyte that plays a vital role in various physiological processes, including maintaining proper nerve function, muscle contraction, and cardiac rhythm. When potassium levels rise excessively, it can lead to serious complications, including cardiac arrhythmias and other muscular and neurological disturbances.

The other options address different conditions or imbalances that do not define hyperkalemia. Low potassium levels represent hypokalemia, high calcium levels pertain to hypercalcemia, and low sodium levels relate to hyponatremia. Therefore, the correct characterization of hyperkalemia focuses on the excess potassium levels in the body.