After taking progesterone for 3 days, there is no menstruation, this situation may be due to the exogenous progesterone has not been metabolized in the body after taking progesterone, retreat bleeding has not yet occurred, and naturally, there will be no menstruation. Taking progesterone to induce menstruation when menstruation does not occur requires 3-5 days of medication if progesterone injections are used, and 7-10 days of medication if oral progesterone capsules are used. Menstruation will not occur until about 3-7 days after stopping the medication, not while taking the medication or just after stopping the medication. Patients can observe for another 3-7 days, if menstruation does not occur after more than a week, on the one hand, it is considered that the endometrium is still relatively thin, proliferation is not good, can not be from the proliferative phase into the secretory phase, on the other hand, it is considered to be pregnant. Patients need to go to the hospital in time for blood HCG test and pelvic ultrasonography in order to clarify the exact cause.