Tamoxifen can be used mainly for patients with breast cancer. In the process of using it, one should pay attention to the side effects, such as patients may experience a transient increase in bone and tumor pain at the beginning of the treatment, and the pain can be gradually reduced by continuing the treatment. In addition, the more common side effects of tamoxifen include gastrointestinal reactions such as loss of appetite, nausea, vomiting, diarrhea, etc. It may also cause patients to experience reproductive side effects, including menstrual disorders, amenorrhea, vaginal bleeding, vulvar itching, endometrial hyperplasia and other related symptoms. In addition, it may also lead to facial flushing, rash, hair loss, and in some patients, leukopenia and thrombocytopenia, and may also affect liver function. In conclusion, the main side effects of tamoxifen are more common in the gastrointestinal tract and reproductive system.