How many clotting factors are required for blood to clot?

Blood clotting involves a complex cascade of events called the coagulation cascade, requiring the activation of multiple clotting factors to form a stable blood clot. The traditional view proposes that it requires the activation of 13 distinct clotting factors (numbered with Roman numerals I to XIII).

When blood vessel damage occurs, the coagulation cascade is initiated, starting with the activation of factor XII. Activation of these factors involves a series of enzymatic reactions, where activated factors convert inactive factors into their active forms. As the cascade progresses, it eventually leads to the activation of thrombin.

Thrombin then converts fibrinogen (a soluble protein present in blood plasma) into fibrin. Fibrin molecules come together to form a mesh-like network, entangling platelets and red blood cells to form a clot or thrombus that plugs the damaged blood vessel and stops the bleeding.

So, the traditional understanding suggests that it takes the activation of all 13 clotting factors in a well-coordinated manner to lead to the formation of a stable blood clot.