Progesterone is a progestin that mainly promotes the transformation of the endometrium, which will cause delayed menstrual cycle and thickening of the endometrium. However, 3-7 days after taking progesterone, there will be medicated withdrawal bleeding, which is equivalent to a menstrual flow. The time of the next menstrual flow should be calculated according to this bleeding time, not according to the previous menstrual cycle. An occasional dose of progesterone will not affect the menstrual cycle and will not lead to disruption of the menstrual cycle, but must be applied under medical supervision. If you suffer from irregular menstruation, progesterone and estrogen can be applied sequentially to regulate the menstrual cycle and restore it to normal. During the period of taking the medication, it is important to take more rest. If you experience nausea or dizziness, you must go to the hospital and let your doctor check it out and adjust the medication if necessary.