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. Factor IX is produced in the liver and is activated by another protein called Factor XI. A deficiency in Factor IX can lead to a bleeding disorder known as hemophilia B. This condition makes it difficult for the blood to clot properly, resulting in prolonged bleeding after injuries or surgeries. Treatment often involves infusions of synthetic or donated Factor IX to help manage the condition.