Excessive potassium intake can result in severe hyperkalemia and fatal arrhythmias. Potassium-containing supplements are widely available over the counter; however, there have been no prior reports of severe hyperkalemia resulting from intentional overdose of these products. We report the case of a 55-year-old man who developed life-threatening hyperkalemia after ingesting a large quantity of potassiumcontaining supplements purchased online. On presentation, the serum potassium level was 9.0 mEq/L, accompanied by electrocardiographic abnormalities, including peaked T waves and atrioventricular block. Despite initial medical intervention, hyperkalemia persisted, necessitating continuous hemodiafiltration, which rapidly normalized serum potassium levels. This case highlights that even in individuals without underlying renal dysfunction, massive ingestion of commercially available potassium supplements can cause severe hyperkalemia. Therefore, clinicians should consider supplement overdose in the differential diagnosis of unexplained hyperkalemia, and current regulatory approaches to potassium-containing supplements may warrant reconsideration.
