As there are many causes of a painful leg, a doctor cannot diagnose deep vein thrombosis (DVT) by symptoms alone. The doctor will ask you some questions and may undertake a blood test (called a D-dimer test), and will then decide if further tests are required.
Before performing any tests, a doctor will establish the likelihood of a blood clot by asking questions, performing a physical examination, and completing a formalised risk score. If the probability of a DVT is low, a blood test, called a D-dimer test, is performed to rule out the diagnosis. D-dimers are degradation products that are built in the course of thrombus formation and dissolution and whose presence in the blood can be detected. If these tests indicate the probability of a DVT is high, confirmatory imaging, usually ultrasonography, is undertaken to detect the clot.
Further imaging tests include taking X-rays of the veins with the use of contrast agents as well as more sophisticated imaging such as computed tomography (CT) and magnetic resonance imaging (MRI).
Please consult your healthcare professional for further information.