Insulin autoimmune syndrome (IAS) is characterized by hyperinsulinemic hypoglycemia with elevated anti-insulin antibodies. Most commonly observed in the Japanese population, elsewhere it is rare and associated with autoimmune diseases, plasma cell dyscrasias, or sulfhydryl group medications. The active metabolite of clopidogrel has a sulfhydryl group and here we report a case of clopidogrel-induced IAS.A 67-year-old man was admitted with severe hyperinsulinemic hypoglycemia requiring continuous intravenous infusion of 10% dextrose to sustain euglycemia. His symptoms of hypoglycemia had started after commencing dual antiplatelet therapy (including clopidogrel) for ischemic heart disease 9 months earlier. The hypoglycemia was associated with elevated insulin, proinsulin, c-peptide, and anti-insulin antibody titers as well as the HLA-DRB1*04 haplotype. Multiple localizing studies were negative for an insulinoma. A diagnosis of IAS was thus made. Clopidogrel cessation, oral dexamethasone, and diazoxide therapy were not sufficient to safely wean the dextrose infusion. Plasma exchange was ultimately effective.This case highlights a case of severe IAS. Given the ubiquity of clopidogrel, IAS should be remembered as a rare adverse effect.