Methylcobalamin can be taken for a long time. Methylcobalamin is mainly used to nourish peripheral nerves in clinical practice, and it is an endogenous vitamin B12, also called methyl vitamin B12. It can also be used with folic acid to reduce the homocysteine content in blood, and can promote the growth of demyelinated axons of nerves. Therefore, for peripheral neuritis, patients with limb numbness, garter-like sensory disorders, or skin ankylosis can take methylcobalamin for the treatment of nourishing peripheral nerves. It is especially suitable for microcirculatory disorders caused by diabetes and diabetic peripheral neuropathy. However, if it is still ineffective after 1 month of medication or there is an uncomfortable reaction, it is recommended to consult a doctor promptly.