Vitamin b12 tablets are mainly used in megaloblastic anemia, the instructions for the use of dosage for oral, 25 ~ 100μg a day (1 ~ 4 tablets a day), or every other day 50 ~ 200μg (every other day 2 ~ 8 tablets), divided or as directed by the doctor to take. When taking vitamin B12, first of all, you need to pay attention to whether the patient is accompanied by folic acid deficiency, because in the use of vitamin B12 treatment, although it can improve the blood picture, but may also mask the clinical manifestations of folic acid deficiency, so for such patients should pay attention to the simultaneous supplementation of folic acid. Secondly, when vitamin B12 is used to treat megaloblastic anemia, severe hypokalemia may occur, so in the 48 hours between treatments, it is necessary to check the blood potassium in order to find and supplement potassium ions in time; the main adverse reactions are hypokalemia and hyperuricemia, etc., and the contraindications are not yet clear. The above content is for reference only, if patients need to use, please under the guidance of a professional doctor reasonable use of medication.