Vitamin B12 is a necessary vitamin in the process of human tissue metabolism. The average total amount of vitamin B12 in the human body is 2 Mel 5 mg, of which 50% is stored in the liver and released into the blood to form red blood cells when the body needs it. Long-term lack of B12 can lead to pernicious anemia. B12 and folic acid are important fear enzymes in the process of nucleic acid synthesis, which are involved in the synthesis of purine, pyrimidine, nucleic acid and methionine, and can promote the synthesis of alkaloids by methyl transfer. At the same time, it can increase the synthesis of glycogen and eliminate lipids in the liver. Clinically, it is often used as a drug for the treatment of liver disease. The human body needs about 121 micrograms of vitamin B121 a day, and 2 micrograms can be provided in food every day to ensure normal needs. Hydroxycobalt in vitamin B12 can react with cyanide to form cyanobaltic acid, which can eliminate the toxicity of cyanide. Therefore, people with vitamin B12 deficiency are more sensitive to cyanide than ordinary people. Vitamin B12 is mainly used in the treatment of malignant anemia, megaloblastic anemia, anemia caused by anti-folic acid drugs and polyneuritis.