Numbness of the left big toe is commonly caused by herniated intervertebral disc or common peroneal nerve injury, peripheral neuropathy, as follows: 1, herniated intervertebral disc or common peroneal nerve injury: can cause numbness of the left big toe, the patient will also have lumbar pain, activity limitation, and discomfort of the lateral knee, etc., and the location and severity of the lesion can be detected through electromyography. 2, peripheral neuropathy: such as vascular supply disorders or diabetes, can cause lesions of the toe nerves, and the conduction function is impaired, manifested as numbness of the toes. Supply disorders or diabetes, can cause toe nerve lesions, conduction dysfunction, manifested as numbness of the toes, in which diabetic patients symptoms are more obvious, and not easy to treat. The above reasons are the common causes of numbness of the left big toe, timely diagnosis, timely treatment can make the symptoms be relieved, but may not be able to completely cure.