Mecobalamin is an activated, endogenous vitamin B₁₂ that is physiologically active and can exert physiological effects by entering the bloodstream directly after oral or intravenous administration. Its primary role is to treat megaloblastic anemia, treat peripheral neuropathy, and nourish peripheral nerves. Adverse reactions to methylcobalamin include occasional rash, headache, feverish sensation, sweating, pain and hardness at the site of intramuscular injection, and can cause severe allergic reactions such as decreased blood pressure and dyspnea. It is contraindicated in patients who are allergic to the drug. If it is ineffective for more than one month, there is no need to continue taking it. Methylcobalamin is a vitamin B₁₂, patients should apply the drug under the advice of a doctor and avoid using the drug on their own.