Severe Recurrent Hyperinsulinemic Hypoglycemia Associated with Quetiapine in a Patient with Schizophrenia: A Case Report

Abstract

Atypical antipsychotics are frequently associated with metabolic disturbances such as weight gain, insulin resistance, and hyperglycemia. In contrast, drug-induced hypoglycemia is rarely described, particularly with quetiapine. We report a case of severe, recurrent hyperinsulinemic hypoglycemia temporally associated with quetiapine use in a patient with schizophrenia, with resolution following drug withdrawal. A 72-year-old man with schizophrenia was admitted for acute psychotic decompensation while receiving long-term haloperidol and quetiapine 150 mg/day. Shortly after admission, he developed recurrent, predominantly postprandial hyperinsulinemic hypoglycemia, with plasma glucose reaching 20–40 mg/dL, repeatedly asymptomatic. During a documented episode (glucose of 48 mg/dL), insulin and C-peptide were inappropriately elevated, confirming endogenous hyperinsulinemia. Adrenal insufficiency, hypothyroidism, insulinoma, IGF-2–secreting tumors, nesidioblastosis, hepatic dysfunction, and factitious hypoglycemia were systematically investigated, with no findings supporting these alternative diagnoses. Hypoglycemia resolved promptly after quetiapine discontinuation and recurred upon rechallenge. Replacement with tiapride led to full metabolic stabilization, with no further hypoglycemic events. This case highlights a rare but potentially life-threatening adverse effect of quetiapine. Clinicians should remain vigilant for hypoglycemia in susceptible individuals, particularly older patients or those with underlying glucose dysregulation, as early recognition and drug withdrawal can prevent serious complications.