Hyperkalemia is a condition where the serum potassium concentration exceeds 5.5 millimoles per liter. Common causes include excessive intake of potassium, such as high-dose potassium penicillin intravenous infusion, ingestion of potassium-containing medications, or transfusion of large amounts of stored blood, all of which can lead to hyperkalemia. Additionally, patients with renal failure who experience oliguria or anuria may have reduced potassium excretion. In such cases, inappropriate potassium supplementation or the use of potassium-sparing diuretics can lead to severe hyperkalemia. Lastly, the movement of potassium from inside the cells—during metabolic acidosis and respiratory acidosis—causes ion exchange, leading to hydrogen ions entering the cells while potassium ions leak out, resulting in hyperkalemia.