Vitamin B12 is a group B vitamin and is currently used as a common clinical drug for the treatment of megaloblastic anemia and neurological disorders. When taking it, care needs to be taken to test the blood potassium, especially in patients treated for megaloblastic anemia. Therefore, it must be taken under the guidance of the instructions and the advice of a medical professional. For conditions that have a high probability of causing hypokalemia, it is important to pay attention to the testing of blood potassium concentration during treatment. Because this drug still has certain side effects, you should not make the mistake of thinking that you can take it for a long time as long as it is a vitamin, as overdosing may lead to allergic rashes and other adverse reactions.