Lower extremity DVT usually takes 30 days to pass through the danger phase. According to the Clinical Guidelines for the Diagnosis and Treatment of Deep Vein Thrombosis (Third Edition), patients with lower extremity DVT of less than 14 days’ duration are considered to be in the acute phase, and those with a duration of 14 to 30 days are considered to be in the subacute phase. Until the chronic phase, patients are at some risk for acute pulmonary embolism. In the acute phase, DVT of the lower extremities has a high rate of pulmonary infarction and mortality, and patients often seek medical treatment for acute pain and swelling of the lower extremities. Some patients are prone to DVT due to delayed medical treatment and inability to give timely and effective treatment in the acute phase. The subacute phase, although more stable than the acute phase, may still lead to pulmonary embolism, resulting in death. If you suffer from lower extremity DVT or experience the above symptoms, you must go to the hospital as soon as possible for examination and treatment under the guidance of your doctor without delay, as this may cause life-threatening situations.