Vitamin B12 includes three kinds of injections, tablets and eye drops, which can cure vitamin B12 deficiency, megaloblastic anemia, neuritis and eyestrain. 1. Vitamin B12 injection: used for megaloblastic anemia due to internal factor deficiency, also used for subacute combined degenerative neurological lesions, such as neuritis adjuvant therapy. Intramuscular injection can occasionally cause rash, itching, diarrhea and allergic asthma, but the incidence is relatively low, and anaphylactic shock can occur in rare cases. 2. Vitamin B12 tablets: used in megaloblastic anemia. Adverse reactions such as hypokalemia and hyperuricemia may occur. 3. Vitamin B12 eye drops: for eye fatigue and other eye discomfort. It is well tolerated, with rare adverse reactions and occasional allergic reactions. It should be noted that vitamin B12 can cause allergic reactions, even anaphylactic shock, and should not be abused. Gout patients using this product may occur hyperuricemia. The use of the drug should be under the supervision of a doctor.