Hypokalemia is common and can be associated with serious adverse consequences, including paralysis, ileus, cardiac arrhythmias, and death. As a result, the body maintains serum potassium concentration within very narrow limits by tightly regulated feedback and feed-forward systems. Whereas the consequences of symptomatic hypokalemia and severe potassium depletion are well appreciated, chronic mild hypokalemia can accelerate the progression of chronic kidney disease, exacerbate systemic hypertension, and increase mortality. Persistent hypokalemia may reflect total-body potassium depletion or increased renal potassium clearance. In a patient with simple potassium depletion, potassium replacement therapy should correct serum potassium concentration, but may have little effect when renal potassium clearance is abnormally increased from potassium wasting. In such cases, the addition of potassium-sparing diuretics might be helpful. Serum potassium concentration is an inaccurate marker of total-body potassium deficit. Mild hypokalemia may be associated with significant total-body potassium deficits and conversely, total-body potassium stores can be normal in patients with hypokalemia due to redistribution. The speed and extent of potassium replacement should be dictated by the clinical picture and guided by frequent reassessment of serum potassium concentration(.) The goals of therapy should be to correct a potassium deficit, if present, without provoking hyperkalemia. Oral replacement is preferred except when there is no functioning bowel or in the setting of electrocardiogram changes, neurologic symptoms, cardiac ischemia, or digitalis therapy.