Derangements in potassium homeostasis affect the body's bioelectric processes, including muscle contraction, nerve conduction, and myocardial electric pacing. Changes in extracellular potassium concentration occur with altered routes of elimination (renal or gastrointestinal) or with pathologic shifts in potassium from one body fluid compartment to another. The therapeutic interventions may either restore a normal resting potential for excitable cells or affect the threshold potential. Thus, an understanding of the basic pathophysiology is the foundation for treatment.