Methylcobalamin is a kind of endogenous vitamin B12, which mainly exists in bone marrow and blood, and is a kind of nerve-nourishing drug that can promote the recovery of nerve function and accelerate the nerve conduction function. Methylcobalamin can be injected and diluted with physiological saline for intravenous injection, and it can also be injected intramuscularly and taken orally, and it is mainly used for the treatment of peripheral neuropathy and megaloblastic anemia caused by vitamin B12 deficiency. Adverse reactions may occur after the use of methylcobalamin, such as skin rash, pain at the injection site and decrease in blood pressure. Moreover, people who work with mercury and its compounds should not use methylcobalamin for a long time and should not inject it at the same site for a long time to prevent the occurrence of hard knots and serious pain, and those who can take it orally should preferably take it orally.