How long it is appropriate to take vitamin B12 depends on the disease caused by vitamin B12 deficiency and the severity of the condition. Vitamin B12 deficiency can lead to a variety of diseases, the most common being megaloblastic anemia, Wernicke’s encephalopathy, as well as neuritis demyelinating changes, neuritis affecting neurointelligence, etc. The time taken varies with the disease and its severity. If the patient is suffering from Wernicke’s encephalopathy, the initial application of vitamin B12 is usually required for intramuscular injection, and the maintenance period should be at least about 1-3 months, and long-term application may be required for patients who drink alcohol. In the case of megaloblastic anemia due to vitamin B12 deficiency, it may need to be applied for at least 3-6 months, with appropriate extension or shortening depending on the severity of the condition. In addition, vitamin B12 must be taken according to the characteristics of your disease and under the guidance of a doctor.