Diagnosis

To diagnose deep vein thrombosis, your doctor will ask you about your symptoms. You'll also have a physical exam so that your doctor can check for areas of swelling, tenderness or discoloration on your skin. Depending on how likely you are to have a blood clot, your doctor might suggest tests, including:

  • Ultrasound. A wandlike device (transducer) placed over the part of your body where there's a clot sends sound waves into the area. As the sound waves travel through your tissue and reflect back, a computer transforms the waves into a moving image on a video screen. A clot might be visible in the image.

    Sometimes a series of ultrasounds are done over several days to determine whether a blood clot is growing or to check for a new one.

  • Blood test. Almost all people who develop severe deep vein thrombosis have an elevated blood level of a substance called D dimer.
  • Venography. A dye is injected into a large vein in your foot or ankle. An X-ray creates an image of the veins in your legs and feet, to look for clots. However, less invasive methods of diagnosis, such as ultrasound, can usually confirm the diagnosis.
  • CT or MRI scans. Either can provide visual images of your veins and might show if you have a clot. Sometimes these scans performed for other reasons reveal a clot.