Deep vein thrombosis is a medical condition characterized by blood clot formation in any deep veins of the body; usually occurring on the leg. The condition is considered as a serious condition because there is a possibility that it may lead to pulmonary embolism caused by a blood clot that had travelled and reached the lung.

Ultrasound is often used to determine the presence and growth of blood clots. CT scan and MRI may show the presence of blood clots by providing visual images of the veins. Venography involves injecting a dye and x-ray procedure to look for clots.

Medications such as blood thinners and thrombolytics are often used in the treatment of deep vein thrombosis aimed at preventing the clot from getting bigger and breaking the clot respectively.

Presence of deep vein thrombosis is often manifested by swelling in the ankles and feet of the affected legs causing cramping pain in the leg originating from the calf. Redness and warmth is remarkable on the affected leg. If it affects other parts of the body an obvious swelling will be observed on the affected portion. If the blood clot had reached the lung (pulmonary embolism); chest pain, feeling lightheaded and fainting, coughing up blood, and sudden onset of shortness of breath which is unexplainable are considered as warning signs for emergency.

The cause of deep vein thrombosis is blood clot formation in the veins deep in the body.