Factor XIII, also known as fibrin-stabilizing factor, is a protein involved in the final stages of blood clotting. Once a clot forms, Factor XIII helps stabilize it by cross-linking fibrin strands, making the clot stronger and more resistant to premature breakdown. This is essential for the clot’s effectiveness in stopping bleeding.

A Factor XIII test measures the activity or levels of this clotting factor in the blood. Low levels of Factor XIII can lead to bleeding disorders, as the clot may not be stable enough to prevent excessive bleeding. This test is used to diagnose Factor XIII deficiency, a rare but serious condition that can cause prolonged or spontaneous bleeding episodes. It is also used to monitor individuals with known clotting disorders or to assess their risk before surgical procedures.