Progesterone needs to be taken orally for 3-5 consecutive days and withdrawal bleeding occurs 3-7 days after discontinuation, up to a maximum of 10 days. Progesterone is a hormonal drug that regulates menstruation. Taking progesterone can help identify whether or not you are pregnant, and identify the cause of irregular menstruation, or even amenorrhea. Depending on the patient’s condition, withdrawal bleeding, equivalent to a menstrual flow, usually occurs after 3-5 days of administration and 3-7 days of discontinuation, up to a maximum of 10 days. If no menstrual flow occurs after the above mentioned time, it is necessary to go to the hospital and have an ultrasound to check the thickness of the endometrium, if the endometrium is around 1.0cm, it indicates that menstruation will come in the near future. If necessary, a urine hCG test can be done to rule out the possibility of pregnancy or a blood test for sex hormone 6 to rule out the possibility of premature ovarian failure. Progesterone is a prescription drug and should only be taken with the appropriate indication and under the guidance of a doctor in strict accordance with the specifications. At the same time, after the occurrence of withdrawal bleeding, a timely review should be conducted so that the dose of the drug can be adjusted.