How long it takes for a blood clot to dissolve varies from person to person, depending on the site of the clot, the time of clot formation, the condition of the patient’s platelets and other factors. The main cause of thrombosis is the increase of blood viscosity, which leads to the accumulation of platelets and the formation of emboli blocking blood vessels, thus causing clinical symptoms of tissue and organ ischemia. For cerebral thrombosis, if the patient’s onset time is within 6 hours, timely thrombolytic therapy can completely melt off the thrombus in some patients. For old thrombosis, the thrombus is hard and firmly adhered to the blood vessel wall, which is usually more difficult to be absorbed. Patients can take oral aspirin, warfarin and other anticoagulant drugs for three months to help reduce the progress of thrombosis. Patients need to maintain a good lifestyle, quit smoking and drinking, and eat a balanced diet to reduce the viscosity of blood, which can help prevent the occurrence and development of thrombosis.