Coagulation tests, also known as blood clotting tests, measure your blood's ability to clot. These tests are important for diagnosing bleeding disorders, monitoring anticoagulant therapy (blood thinners), and assessing risk before surgery. Common Coagulation Tests: Prothrombin Time (PT): Measures how long it takes for blood to clot. Often reported as an INR (International Normalized Ratio). Activated Partial Thromboplastin Time (aPTT): Another test that measures how long it takes for blood to clot. Platelet Count: Measures the number of platelets in your blood, which are essential for blood clotting. Fibrinogen: Measures the amount of fibrinogen, a protein involved in blood clot formation. D-dimer: Measures the amount of D-dimer, a protein fragment produced when a blood clot breaks down.