Methylcobalamin and vitamin B12 are different in terms of drug type, indications, adverse reactions and contraindications. 1. Types of drugs: methylcobalamin belongs to coenzyme drugs; vitamin B12 belongs to vitamin drugs. 2. Indications: methylcobalamin is usually used in the treatment of peripheral neuropathy; vitamin B12 is usually used in the treatment of megaloblastic anemia, and can also be used in the treatment of subacute combined degenerative neuropathy. 3. Adverse reactions: Methylcobalamin may cause loss of appetite, nausea, diarrhea, rash and other adverse reactions; vitamin B12 may cause rash, itching, diarrhea, hypokalemia and other uncomfortable symptoms after the use of vitamin B12. 4. Contraindications: prohibited for patients who are allergic to methylcobalamin and its excipients; prohibited for patients who are allergic to vitamin B12, glaucoma, ophthalmic allergy. It is recommended to use the drug strictly under the guidance of a physician.