The test measures the substance that the body releases after a blood clot breaks up, referred to as D-dimer. Low levels of D-dimer mean a patient probably does not have blood clotting issues. An elevated level of D-dimer has a few causes. Serious blood clotting problems, such as pulmonary embolism, which is life threatening, can result in high levels of D-dimer. A patient with high D-dimer levels may also have disseminated intravascular coagulation (DIC), another serious condition that prevents blood from clotting as it should. Unchecked pulmonary embolism, deep vein thrombosis and DIC can kill patients, notes WebMD.