There are many reasons for not having a period all the time, such as: first, physiological factors should be considered. For women of childbearing age, they need to exclude whether they have early intrauterine pregnancy, regular menstruation, and if they have not had a period for 40 days, they need to go to the hospital to check urine pregnancy or blood HCG to determine whether they are pregnant. If pregnancy is determined, it is normal not to have a period. Secondly, pathological causes such as polycystic ovary syndrome, pituitary tumor, hyperlactatemia, post-abortion induced uterine adhesions, endometrial tuberculosis, etc. can cause absence of menstruation. Finally, menopausal women may also experience irregular menstruation due to reduced ovarian function and near menopause, with menstruation occurring once every three to four months or six months. If there are pathological changes, you need to go to the hospital in time and get the right treatment under the guidance of the doctor.