These conditions can increase your risk of a deep vein thrombosis: Having an inherited (genetic) condition increases your risk of blood clots. Having cancer and some of its treatments (chemotherapy). Having a history of deep vein thrombosis in yourself or your family. Having limited blood flow in a deep vein because of an injury, surgery or immobilization. Not moving for long periods of time, like sitting for a long time on trips in a car, truck, bus, train or airplane or being immobile after surgery or a serious injury. Being pregnant or having recently delivered a baby. Being older than 40 (although a DVT can affect people of any age). Having overweight/obesity. Having an autoimmune disease, like lupus, vasculitis or inflammatory bowel disease. Using tobacco products. Having varicose veins. Taking birth control pills or hormone therapy. Having a central venous catheter or pacemaker. Having COVID-19.