Immunoglobulin therapy is therapy with antibody (immunoglobulin) mixtures, given via intravenous, subcutaneous, or intramuscular routes of administration, used to treat or prevent a variety of diseases. Immunoglobulin as used in infusions contains the pooled polyvalent IgG antibodies extracted from the plasma of thousands of blood donors. The effects of immunoglobulin generally last between two weeks and three months, although most subcutaneous brands of immunoglobulin are designed to be administered 1–2 times a week, and for most purposes intravenous immunoglobulin is administered once every 3–4 weeks. One currently marketed preparation of subcutaneous immunoglobulin, HyQvia, uses hyaluronidase in order to allow for greater injection volumes and thus less frequent administration times than other forms of subcutaneous immunoglobulin (once every 3–4 weeks.) Additionally, some diseases, such as myasthenia gravis may only require immunoglobulin treatment once every 3–4 months.