Administration of hydroxocobalamin in the three years before enrollment Patients with active, uncontrolled psychiatric disorders Severe neurologic deficit Known hematologic malignancy Known coagulation disorder that contraindicates intramuscular injection End-stage kidney disease (GFR <15ml/min) Chronic liver disease (Child-Pugh B or C) Pregnant patients Known infection of Hepatitis B or C and HIV Diagnosis of myelodysplastic syndrome