Storage-stable blood coagulation factor acting in the intrinsic pathway of blood coagulation. Its activated form, IXa, forms a complex with factor VIII and calcium on platelet factor 3 to activate factor X to Xa. Deficiency of factor IX results in HEMOPHILIA B (Christmas Disease).

Synonyms: Factor IX Complex, Factor Nine, Coagulation Factor IX, Blood-coagulation factor IX, Autoprothrombin II, 9001-28-9, Factor IX, Christmas Factor, Plasma Thromboplastin Component, Factor IX Fraction, Blood Coagulation Factor IX, Factor IX, Coagulation, Factor 9