Most of the nausea and abdominal pain before menstruation are caused by changes in hormone levels before menstruation. During this period, hormone levels are at a high level, causing a series of uncomfortable symptoms in women, such as loss of appetite, dizziness, insomnia, breast swelling, nausea, abdominal pain and other premenstrual symptoms, most of which are physiological and do not need to be overly concerned. If a woman does not use contraception, nausea and abdominal pain cannot be ruled out as a result of pregnancy, and it is recommended that a blood HCG test be performed to rule out the possibility of pregnancy.