The most common risk factor for venous thromboembolism is immobility. When you are unable to move, blood clots have an increased chance of forming in your veins. This is because your veins aren't able to pump the blood the way they should when you are not moving. Factors that can contribute to immobility include long-distance travel, prolonged bed rest, surgery, certain medical conditions, and certain medications. Other risk factors for venous thromboembolism include age, obesity, certain medical conditions, certain medications, smoking, and a history of blood clots. It is important to be aware of these risk factors and take steps to reduce your risk of developing a venous thromboembolism. This can include exercising regularly, eating a balanced diet, maintaining a healthy weight, and avoiding smoking.