Potassium plays an important role in cell metabolism and membrane excitability. Disorders of potassium balance can have profound clinical effects, particularly on the cardiovascular and neuromuscular systems. Chronic hyperkalemia invariably results from impaired renal potassium excretion. Hyperkalemia can be a potentially life-threatening disturbance requiring emergency intervention. Treatment is usually directed at correcting the defect in potassium excretion. Hypokalemia has become closely linked with in cats. Clinical signs include muscle weakness and renal dysfunction, which usually respond well to oral potassium supplementation.