A. There is no need to be anxious about the recurrence of thrombosis during anticoagulation therapy, we should carefully analyze the causes and make active management: 1. The recurrence of deep vein thrombosis (DVT) or pulmonary embolism (PE) is less frequent when anticoagulant drugs are used according to the therapeutic dose. The most common reason for thrombotic recurrence when treated with vitamin K antagonists (VKA) such as warfarin or direct new oral anticoagulants (DOAC, such as rivaroxaban, apixaban, dabigatran, etc.) is failure to take the medication as prescribed, and missed doses of DOAC increase the risk of thrombotic recurrence. Patients with recurrent thrombosis on VKA should first be evaluated for INR compliance at the time of recurrence and prior to recurrence, and in most cases INR is not met; the most likely cause is that the patient did not take the medication as prescribed. Inadequate anticoagulation therapy to overcome hypercoagulability is a possible cause of thromboembolic recurrence. The risk of VTE recurrence is 3 times higher in cancer patients than in non-cancer patients, and 80% of thrombosis occurs when anticoagulation is achieved. If VKA anticoagulation therapy fails suggesting the possible presence of undetected malignancy, other conditions such as anatomical abnormalities (May-Thurner syndrome), myeloproliferative neoplasms, and paroxysmal sleep hemoglobinuria are also high risk factors for DVT recurrence. 3. In patients with antiphospholipid antibody syndrome, thrombotic recurrence is associated with inadequate anticoagulation due to pseudo-attainment of INR, which is associated with lupus anticoagulant interference with INR detection, and it is difficult to clarify true anticoagulation if lupus anticoagulant prolongs baseline PT levels. In addition the presence of recurrent DVT during treatment with heparin should be noted for conditions such as heparin-induced thrombocytopenia. Second, how to treat recurrent DVT during anticoagulation therapy: 1, for those who do not meet the INR standard immediately start adequate low-molecular heparin (LMWH) therapy, if still using VKAs as long-term treatment, the quality of anticoagulation therapy should be enhanced, such as intensive counseling, shorten the INR monitoring interval, etc., if the effect of VKA therapy is not satisfactory can be considered to switch to DOAC therapy. 2.Recurrence of DVT during treatment with DOAC should be treated with LMWH and then given VKA with INR up to 2-3. 3.Recurrence of DVT despite INR≥2 during VKA treatment should be given vitamin K followed by full dose LMWH treatment, if confirmed as cancer patients should continue LMWH treatment, if recurrence of DVT occurs again during full dose LMWH treatment, the LMWH dose one-third to one-fourth. 4. Non-cancer patients with recurrence despite adequate anticoagulation should pay attention to finding other causes and pay attention to phenomena such as platelet elevation, and may choose long-term LMWH, LMWH followed by VKA, LMWH followed by VKA combined with aspirin or Juanda hepatic deca sodium treatment.