Intravenous immune globulin (IVIG) is a sterile solution of human IgG (with trace IgA/IgM), derived from pooled plasma of thousands of donors. It’s administered primarily to treat or prevent immunodeficiencies, autoimmune and inflammatory disorders. For chronic therapy, dosing is weight-based (300–800 mg/kg every 3–4 weeks), with adjustments for high BMI. Subcutaneous options are dosed by converting IV regimens (multiply by 1.37, divide by dosing interval), typically administered weekly, starting one week after the last IV dose.