Vitamin B12 is mainly used in the treatment of megaloblastic anemia, and the number of times a day it should be taken should be specified according to its specifications, usually about 1-4 times a day. 1. 25 μg of vitamin B12: Oral, 25-100 μg a day (1-4 tablets a day), or 50-200 μg every other day (2-8 tablets every other day), in divided doses, or as directed by a doctor. 2. 50 μg of vitamin B12: Oral, 25-100 μg (0.5-2 tablets) a day or 50-200 μg (1-4 tablets) every other day, in divided doses or as directed by a doctor. 3. The reactions of pregnant and lactating women, children and the elderly are not clear; the contraindications to the use of the drug are not clear; there are reports of adverse reactions such as hypokalemia and hyperuricemia. It is recommended to take the drug under the guidance of professional doctors, do not blindly change the dosage and the number of times of taking the drug.