The recommended dosage of vitamin B12 instructions are: tablets, oral, 25-100 μg a day or 50-200 μg every other day, in divided doses; injection: intramuscular injection, 0.025-0.1 mg a day or 0.05-0.2 mg every other day; eye drops: eye drops, 1-2 drops each time, 3-5 times a day. This product can be used for megaloblastic anemia and adjuvant treatment of neuritis. Vitamin B12 may cause hypokalemia and hyperuricemia and other adverse reactions, intramuscular injection may occasionally cause rash, itching, diarrhea and allergic asthma; eye drops may cause allergic reactions in the eye. Note that this product is prohibited for those who are allergic to the product. Eye drops should be used with caution in patients with glaucoma, and attention should be paid to the detection of blood potassium level after injection. Patients must use the drug under the guidance of a professional physician, not to use the drug at will, and strictly comply with the doctor’s instructions.