45 years old irregular menstruation small stomach pain may be a physiological phenomenon caused by perimenopausal syndrome, may also be uterine fibroids, endometriosis and other diseases caused by the cause of the need to take medication, other treatments, surgical treatment, part of the patient does not need to be treated. 1. Perimenopausal syndrome: caused by hormonal abnormalities before and after menopause, it can be manifested as menstrual disorders, abdominal pain and so on. If the symptoms are severe, estrogen drugs such as estradiol valerate and estradiol drospirenone tablets, or progesterone drugs such as dydrogesterone and micronized progesterone can be used as prescribed by the doctor. 2. Uterine fibroids: common symptoms include abnormal menstruation, abdominal pain, increased leukorrhea, etc. Patients need to apply mifepristone as prescribed by the doctor. The patient may also need to follow the doctor’s instructions to apply the contraceptive pill such as compound norethindrone tablets and compound methyl norethindrone tablets. Other treatments such as uterine artery embolization and high-energy focused ultrasound are also available. For those whose fibroid is too large and drug treatment is ineffective, surgical treatments such as myomectomy and hysterectomy should be considered. 3. Endometriosis: patients will have abnormal menstruation, dysmenorrhea, acute abdominal pain and other symptoms. They need to take non-steroidal anti-inflammatory drugs such as indomethacin and ibuprofen, gonadotropin-releasing hormone agonists such as leuprolide and goserelin, and progestational drugs such as pregnenolone and medroxyprogesterone, as prescribed by the doctor. In cases where medication is ineffective, conservative surgery and radical surgery are required. Those with perimenopausal syndrome and endometriosis, which generally have mild symptoms, as well as those with fibroids that are small in size, do not need to be treated, but need to be followed up on a regular basis. It is recommended that patients with irregular menstrual periods and small stomach pain at the age of 45 should go to the hospital to clarify the cause of the disease and actively treat the original disease.