Hypokalemia is a condition of low serum potassium (K+) concentration. The normal range of serum K+ is 3.5-5.0 mEq/L. This is one of the most common electrolyte derangements in the hospital setting. There is a broad differential for the underlying etiology of hypokalemia, but most causes fall within the broad categories of K+ losses, redistributive hypokalemia (influx of K+ to the intracellular space), or insufficient K+ intake.

Conditions that contribute to K+ losses are excessive K+ urinary output and prolonged vomiting or diarrhea. Other causes include laxative abuse, diuretics, salicylates, tumors (ie, VIPoma, villous adenoma), burns, malnutrition, alcohol use disorder, excessive sweating, jejunoileal bypass, and renal tubular disease. Chemotherapy and radiation as well as a variety of medication classes can contribute to excessive potassium loss. These include bronchodilators, caffeine, mineralocorticoids, glucocorticoids, and penicillin in high doses. Excessive consumption of natural licorice is a less common cause.

Conditions that contribute to increased transfer of potassium into the cells are excessive insulin, insulin administered with dextrose or glucose (rather than saline solution), refeeding syndrome, and other drug-induced agents that elevate beta-adrenergic activity. Additional causes include hypothermia, alkalosis, increased extracellular pH, and toxicity of chloroquine, barium, and similar agents. Hypokalemic periodic paralysis is an autosomal dominant inherited disorder that can cause episodic muscle weakness when K+ levels are low.

Conditions that contribute to decreased K+ intake include potassium-deficient diet, parenteral therapy, and malnutrition. These conditions are usually seen in combination with other factors in patients with hypokalemia.