Melatonin is a hormone secreted by the pineal gland in the body, and its secretion value is at its peak at night, which has a certain sleep-aiding effect. Since melatonin is a hormone normally secreted by the body, there are generally no side effects or contraindications. However, if exogenous supplementation is carried out, the dose used cannot be controlled, and improper use can cause certain side effects, and there are certain contraindications when used by special groups. I. Side effects: If you are using commercially available melatonin products, the dose of melatonin in such items may exceed the body’s daily requirement, so the use can cause certain side effects. Such as melatonin can inhibit the secretion of gonadal hormones, if taken in excess may lead to drowsiness, dizziness, decreased libido and other side effects, but also can appear to lower body temperature and other performance. Second, contraindications: 1, minors: if children or adolescents insomnia, usually not recommended to take melatonin, because it can affect the gonadal axis hormone secretion, if insufficient secretion of sex hormones, can lead to reproductive organs and dysfunction; 2, pregnant and lactating women: if pregnant or lactating women, the use of melatonin products will also affect the body’s hormone secretion, which in turn may affect fetal development or lactation; 3, patients with endocrine diseases: such as diabetic patients, patients with abnormal thyroid function and other groups, the use of melatonin may further affect the endocrine function and aggravate the condition; 4, patients with underlying organ dysfunction: especially patients with liver and kidney insufficiency, the ability to metabolize drugs is limited, taking melatonin may increase the burden on the liver and kidneys. In addition, during the taking of melatonin should pay attention to the prohibition of alcohol consumption, and strictly in accordance with the instructions of the doctor, not to take or change the dosage of drugs, to avoid overdose caused by discomfort.