Numbness of the left leg when walking may be caused by a variety of reasons, such as lumbar disc herniation, varicose veins in the lower limbs, cerebrovascular disease, neuritis, etc. It is recommended that you go to the hospital to do a targeted examination and then treat the cause. The common causes of numbness in the left leg when walking are as follows. 1. Herniated lumbar intervertebral disc, the herniated intervertebral disc can compress the nerve root, resulting in numbness of the lower limbs. The treatment should be based on the specific situation, to choose the drug or surgical treatment. 2. Varicose veins in the lower limbs can lead to lower limb acidity, edema and fatigue, sometimes there will be leg muscle spasms, and many patients will also appear in the lower limb numbness. Depending on the specific disease, you can choose compression therapy, drug therapy or surgical treatment. 3. Cerebral infarction and other cerebrovascular diseases often have numbness of the lower limbs, the treatment is based on internal conservative treatment, the use of some drugs to improve cerebral circulation, symptomatic anti-brain edema, reduce intracranial pressure, etc., serious surgical treatment. 4. Diabetes and other chronic diseases caused by neuritis, as well as neuritis peripheral nerve lesions can also lead to leg numbness. Therefore, the situation of numbness in the left leg when walking must be timely medical treatment, according to the diagnosis to determine the treatment program.