A 41-year-old unemployed, single woman with suspected insulinoma and a 13-year history of refractory schizophrenia (diagnosed according to The Diagnostic and Statistical Manual of Mental Disorders IV Criteria) was transferred from a mental hospital to the inpatient psychiatric unit of the Osaka General Medical Center (OGMC) for persistent hypoglycemia (fasting plasma glucose = 50~60 mg/dL) combined with elevated levels of immunoreactive insulin (IRI; 12.7 μU/mL) and C-peptide immunoreactivity (CPR; 4.1 ng/mL). Here, INS is linked to pancreatic insulinoma.