| Surgery |
| Trauma (major trauma or lower-extremity injury) |
| Immobility, lower-extremity paresis |
| Cancer (active or occult) |
| Cancer therapy (hormonal, chemotherapy, angiogenesis inhibitors, radiotherapy) |
| Venous compression (tumor, hematoma, arterial abnormality) |
| Previous VTE |
| Increasing age |
| Pregnancy and the postpartum period |
| Estrogen-containing oral contraceptives or hormone replacement therapy |
| Selective estrogen receptor modulators |
| Erythropoiesis-stimulating agents |
| Acute medical illness |
| Inflammatory bowel disease |
| Nephrotic syndrome |
| Myeloproliferative disorders |
| Paroxysmal nocturnal hemoglobinuria |
| Obesity |
| Central venous catheterization |
| Inherited or acquired thrombophilia |