Causes of leg weakness include lumbar spine disease, hypokalemia, vascular disease, hypoglycemia, and hypothyroidism. 1. Lumbar spine diseases, such as lumbar disc herniation or lumbar spinal stenosis, if compression of nerves can appear symptoms of leg weakness, weakness and numbness of lower limbs. Lumbar spine MRI films can be used to make a clear diagnosis. 2. Hypokalemia, which is caused by insufficient intake or excessive loss of potassium, will lead to weakness of both lower limbs, which can be diagnosed clearly through blood potassium test, and the symptoms can be relieved after potassium supplementation. 3. Lower limb vascular diseases, such as thromboembolic vasculitis, can cause reduction of blood flow to the lower limbs and ischemia of tissues, resulting in weakness of the lower limbs and inability to walk long distance. 4. Hypoglycemia, hypoglycemia can cause weakness of legs, panic and sweating. 5. Hypothyroidism can cause weakness of the legs, and in some cases, there is mucous edema of the lower limbs. These are the specific causes of leg weakness, if the symptoms are serious, you need to go to the hospital.