The rising prevalence of chronic and end-stage kidney disease is accompanied by a concomitant rising risk of hyperkalemia in these patients. Sodium polystyrene sulfonate (Kayexalate, sanofi-aventis, Bridgemater, NJ) is a commonly used treatment of hyperkalemia. We present a case of Kayexalate-induced colonic necrosis as a reminder of this rare, but potentially avoidable, toxicity of a commonly used medication.