Breast cancer patients feeling very sleepy after radiotherapy may be due to the patient’s excessive psychological pressure, or the side effects of radiotherapy. Breast cancer patients generally have more psychological pressure, and may have long-term anxiety, uneasiness, fatigue, etc. Radiation therapy is a kind of treatment with high side effects. Radiation therapy is a kind of treatment with big side effects on human body. After radiation therapy, patients may experience nausea, diarrhea, dizziness, hair loss, etc. Especially for the week after the first radiation therapy, patients may feel tired or lethargic, which is usually a side effect after chemotherapy. Patients should increase rest, maintain a balanced diet, keep good physical condition and active treatment. Discomfort reactions after radiotherapy should be promptly notified to the doctor to identify the causes and treat them.