If there is no disease need, the elderly are not recommended to take vitamin b12 for a long time. vitamin b12 belongs to the drugs, any drug has side effects, long-term use may cause physical damage. Vitamin b12 can promote the maturation of human erythrocytes, alleviate the symptoms of anemia, involved in neuroprotein synthesis, but long-term use, may produce drug tolerance, at the same time prone to adverse reactions, such as rashes, itching, hives, diarrhea, allergic asthma, etc., and a very small number of patients will be anaphylactic shock during the medication. If the treatment of disease need to take vitamin b12, need to be under the guidance of a doctor, if it is to supplement the body nutrients, do not recommend long-term use, can be supplemented by food, such as animal liver, seafood, etc., to reduce the body damage.