Factor XI which is also known as thromboplastin antecedent It is one of the enzymes of the coagulation cascade which is in the zymogen form of factor XIa. Like other coagulation factors, it is a serine protease. The Liver produces Factor XI (FXI), synthesized as a single polypeptide chain, but circulates as a homo-dimer in its inactive form. In case there is any problem with factor XI it results in its deficiency. When the body produces less factor XI than it should, the clotting reaction will be blocked and blood clot does not form, which leads to an inherited bleeding. After the surgery, there will be continuous bleeding which is the most common feature of Factor XI. Bleeding will be there for the surgeries especially involving in inside of mouth and nose. Due to the disruptions or changes to the F11 gene the Factor XI deficiency is caused and can occur in people of either sex.