Side effects of drugs are a kind of adverse drug reactions, which are harmful reactions unrelated to the purpose of treatment that occur during the application of drugs for the prevention, diagnosis or treatment of diseases according to normal usage and dosage. Lysine vitamin B12 granules are compounded preparations with lysine hydrochloride, vitamin B12 and inositol as the main ingredients. Excessive amounts of vitamin B12 can produce toxic side effects. Excessive amounts of vitamin B12 can cause allergic reactions such as asthma, urticaria, eczema, facial puffiness, chills, and can also lead to folic acid deficiency. Lysine vitamin B12 granules are used in doses with few side effects and are contraindicated in people with allergies to amino acids. The dosage is gradually reduced after the child’s appetite improves until the drug is discontinued. Lysine vitamin b12 granules can promote growth and development of children, improve appetite, eliminate xenophagia, help brain development and improve intelligence. Lysine vitamin B12 granules have the effect of anti-anemia, strengthening the body and resistance. It should be noted that the combination of lysine b12 granules with chloramphenicol should be avoided because chloramphenicol can eliminate the hematopoietic effect of vitamin B12. High intake of vitamin C should be avoided when taking lysine b12 granules, as vitamin C can disrupt the absorption of vitamin B12. In addition, lysine vitamin B12 granules are prescription drugs and need to be prescribed by a doctor, so patients should not purchase them on their own.