Potassium, Serum

The Potassium, Serum test (serum potassium, K) is used to confirm and monitor dyskalemias, including hyperkalemia and hypokalemia. It is also ordered after initiation or dose changes of medications that alter potassium balance, such as diuretics, to track levels. Clinicians use this assay to evaluate electrolyte status in chronic conditions associated with potassium shifts, including chronic kidney disease.

Potassium functions with sodium, chloride, and bicarbonate to maintain water distribution, muscle contraction, nerve impulse transmission, and acid–base equilibrium. These coordinated electrolytes support membrane excitability and physiologic stability across tissues. Renal excretion, under the influence of aldosterone, is the primary mechanism governing potassium homeostasis. Because most potassium resides intracellularly, the extracellular and plasma fraction is small; modest changes in serum levels can therefore have outsized physiologic effects. Marked abnormalities produce neuromuscular dysfunction and disturbances of cardiac conduction, with risk of shock, respiratory compromise, and life‑threatening arrhythmias.