Mecobalamin, also known as methylcobalamin, can be used for a long time without side effects. Methylcobalamin, also known as endogenous vitamin B12, can be synthesized and secreted by the human body, and is mainly found in the blood and bone marrow of the human body. If a patient has peripheral nerve injury, the use of methylcobalamin can play a role in nourishing peripheral nerves, and can promote the synthesis and repair of nerve demyelination. Therefore, mecobalamin can be used to treat peripheral neurological diseases, such as numbness and pain of the limbs due to long-term diabetic microcirculation disorder, resulting in peripheral nerve dystrophy and nerve demyelination, and patients can take mecobalamin orally for a long time to improve the symptoms.