Fibrinogen

The Fibrinogen Test, also known as a Factor I assay, is a blood test used to measure the amount of fibrinogen—a vital protein produced by the liver—circulating in your bloodstream. Fibrinogen is the silent architect of blood clotting. When you sustain an injury and begin to bleed, your body triggers a coagulation cascade, a complex series of chemical reactions designed to stop the blood loss.

During this process, an enzyme called thrombin converts inactive fibrinogen into long, sticky strands of fibrin. These strands weave together to form a sturdy mesh that traps platelets and red blood cells, effectively sealing the wound with a stable clot. Physicians typically order this test if you exhibit symptoms of a clotting disorder, such as frequent nosebleeds, excessive bruising, or heavy menstrual cycles.