Factor IX is a protein in the blood that plays a crucial role in the process of blood clotting. It is part of the coagulation cascade, a series of reactions that help stop bleeding when injuries occur. When activated, Factor IX works with other proteins to form a clot, preventing excessive blood loss. Deficiency or dysfunction of Factor IX leads to a bleeding disorder known as hemophilia B. This condition is typically inherited and can result in prolonged bleeding after injuries or surgeries. Treatment often involves infusions of Factor IX concentrates to help manage and prevent bleeding episodes.