How do you know if you have dvt?

Ultrasound. Duplex ultrasound is diagnostic for most dvt's except in the iliac or vena cava where a ct venogram is diagnostic. Symptoms include leg pain and swelling.
Ultrasound. The clinical findings in a patient with deep venous thrombosis consist primarily of swelling. Swelling is typically constant but the other signs are variable. If you have a concern you should have an ultrasound to look for the deep venous thrombosis.
Ultrasound. If you have a history and physical examination that is strongly suggestive of a dvt, a high d-dimer blood test, and an ultrasound that shows lack of compressibility in a vein, you have a dvt.
Pain. Pain and swelling are symptoms. Need to be checked very soon. Ultrasound is needed.
Tricky sometimes. Achy pain and swelling, particularly in the calf/ankle, are the classic symptoms, but many patient actually have no symptoms. Also, if it's both legs, it's probably not dvt. A leg that turns white or blue/purple is an emergency. The first symptoms for some people will actually be chest pain, cough, fast heartbeat and/or shortness of breath from clots going to the lung which is also an emergency.