D-dimer is a common monitoring aid in the case of venous thrombosis. When venous thrombosis is in the acute phase, there is a significant exponential increase in D-dimer. Therefore, a high D-dimer often indicates that the thrombosis is in the acute phase. It is recommended to promptly visit the vascular surgery clinic and have a detailed examination to clarify the diagnosis and specific stage of thrombosis. Since the risk of thrombus dislodgement is high in the acute stage, it is recommended that after clear diagnosis, bed braking, avoiding massage and squeezing the affected limb to prevent thrombus dislodgement and the risk of pulmonary embolism, and adding anticoagulant drugs. Commonly used anticoagulants are warfarin, rivaroxaban, and subcutaneous low-molecular-weight heparin. With standard anticoagulation therapy, the D-dimer will gradually improve and return to normal as the disease progresses. The D-dimer is rechecked about two weeks after treatment to clarify the condition of the disease.