Hemocoagulation, blood coagulation, is an important indicator of hemostatic balance in the human body. There are many ways how to investigate blood clotting. In practice, next to the tests investigating time of coagulation cascade from view of internal way (APTT – activated partial tromboplastin time) and external way (PT – prothrombin time) is often used determining of fibrinogen concentration by Clauss method. Derived fibrinogen method determined fibrinogen concentration, too, by subtracting form the clotting curve in PT test. The reaction for Clauss method is not necessary here. Derived fibrinogen is not used much in practice. This is the reason, why the thesis related to this project will try to find relationship between concentration of fibrinogen and standard tests APTT and PT. Clinical data will be used for this.