Introduction: Lithium is a medication used to treat bipolar disorder. It has a narrow therapeutic index, which frequently causes toxicity in patients.
Case report: We present an unusual case of a 66-year-old female with a history of bipolar disorder on chronic lithium, who developed a third-degree heart block, encephalopathy, and acute renal failure because of lithium toxicity.
Conclusion: This case highlights a rare but life-threatening case of complete heart block in the setting of lithium toxicity. The patient was treated with hemodialysis and pacemaker placement.