Immunoglobulins are large Y-shaped proteins produced by B-cells and plasma cells that are used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. Immunoglobulin G (IgG) preparations are approved by the US Food and Drug Administration for the treatment of primary immunodeficiency disease, idiopathic thrombocytopenic purpura, Kawasaki disease, chronic lymphocytic leukemia with frequent infections, bone marrow transplantation, to prevent infection in pediatric human immunodeficiency virus, and chronic inflammatory demyelinating polyneuropathy. However, IgG products are frequently used off label in many autoimmune conditions. The advent of numerous intravenous and subcutaneous formulations of IgG presents new opportunities impacting patient preferences, site of care, and costs. The appropriate and optimal use of IgG is reviewed based on discussions from an expert roundtable panel and review of the scientific literature. Clinicians and payers should consider patient preferences, evidence- based guidelines, and policies when selecting an IgG product.