Heavy legs and weakness can be caused by the following reasons: First, lower limb vascular disease: varicose veins of the lower limbs or venous insufficiency of the lower limbs can lead to symptoms of heavy legs and weakness, which can be accompanied by swelling of both lower limbs. To check the venous ultrasound of both lower extremities for diagnosis and give early treatment. Secondly, low potassium: Patients with low potassium can have weakness of both lower extremities, pay attention to the blood test, and if there is low potassium, potassium treatment should be given early to increase the strength of both lower extremities. Third, degeneration in old age: elderly people can have heavy and weak legs in aging, which can be accompanied by other symptoms, and should be diagnosed according to the patient’s age and other symptoms such as decreasing function.