Deep vein thrombosis often does not cause symptoms or causes only minimal symptoms. When symptoms occur, they include:

• Swelling.
• Warmth.
• Pain or tenderness. The pain may be in the calf or thigh and may be present only when the affected area is touched or when standing or walking.
• Redness.

There are many other conditions with similar symptoms, such as a ruptured Baker's cyst or cellulitis, which can make diagnosing deep vein thrombosis difficult.

Sometimes life-threatening pulmonary embolism is the first indication that you have deep vein thrombosis. Pulmonary embolism is the sudden blockage of an artery in the lung. Blood clots in the deep veins of the leg are the most common cause of pulmonary embolism. Symptoms of pulmonary embolism include:

• Sudden shortness of breath.
• Chest pain that may get worse with a deep breath.
• A cough that may bring up blood.
• A fast heart rate.
• Fainting (syncope).