The D-dimer test measures levels of D-dimer in the blood, which is a fragment produced when a blood clot dissolves. An elevated D-dimer level may indicate the presence of a blood clotting disorder like deep vein thrombosis, pulmonary embolism, or disseminated intravascular coagulation. The D-dimer test is used to help diagnose these types of blood clotting disorders in patients experiencing related symptoms or who have risk factors. While an elevated D-dimer suggests a clotting disorder, additional imaging tests are needed to confirm the location and type of any clots present.