A d-dimer test is a blood test that measures a substance (fibrin)
that is released as a blood clot breaks up. D-dimer levels are often higher
than normal in people who have a blood clot; but other conditions, such as
cancer, also may cause high d-dimer levels.
A low d-dimer test
result means that a blood clot in the leg or the lung (pulmonary embolism) is
unlikely.