Numbness of the left arm should be treated according to the specific causative factors; common causative factors include cervical spondylosis, diabetic peripheral neuropathy, cerebrovascular disease, etc.; in the treatment of the disease, drugs or physiotherapy should be applied to the primary cause. 1. Cervical spondylosis: If cervical spondylosis leads to local nerve root compression, causing numbness of the left arm, methylcobalamin, vitamin B1 and other drugs can be applied to nourish the nerves, together with local physiotherapy such as massage, acupressure, traction and infrared irradiation, which is conducive to the improvement of local blood circulation and the alleviation of the above symptoms. 2. Diabetic peripheral neuropathy: If the left arm numbness is caused by diabetic peripheral neuropathy, resulting in damage to the peripheral nerves, the main application of glucose-lowering drugs, such as acarbose or insulin, to control blood sugar. Neurotrophic repair drugs such as B vitamins and methylcobalamin should be applied to promote the recovery of damaged nerves and improve the above symptoms. 3. Cerebrovascular disease: If the numbness of the left arm is caused by cerebral infarction, it is mainly for the treatment of the original disease, applying aspirin, clopidogrel and other anti-platelet aggregation drugs, applying riscovastatin, simvastatin and other statins, and applying the two types of drugs together. Numbness of the left arm, if the symptoms continue to be unable to relieve, or the presence of other discomfort manifestations, should be as early as possible to seek medical treatment, through the improvement of relevant examination, diagnosis of the causative factors, give targeted treatment.