If a woman does not have a period, she should first have an ultrasound and blood HCG test to rule out pregnancy-induced absence of menstruation. If the ultrasound indicates that the thickness of the endometrium is more than 1.0 cm, progesterone will usually bring on menstruation. If you stop taking progesterone for 7-10 days and your period is still coming, we should conduct further investigation to find out if you are pregnant or have irregular periods due to ovarian failure, or conduct hysteroscopy to find out if there are adhesions in the uterine cavity that cause irregular periods. Therefore, if a woman does not have a period, she should first undergo the necessary tests to rule out pregnancy and some diseases before performing progesterone treatment.