Hi, I m of the following opinion: i. Regesterone [Noresthisterone] is used to postpone periods, but the dosage depends on the proximity to your natural period, your body weight and the duration of postponement needed, [Usually less daily dosage is advised since higher doses may cause side effects like vomiting, dizziness, breast tenderness, rashes etc., and sometimes may cause breakthrough bleeding.] ii. In best interest, it is wise to ask your PCP for your appropriate dose, where the dose should be continued until you need it or for a maximum of two weeks, Withdrawal bleeding is usually seen 3-7 days after the completion of the course. PS. Regesterone can also cause changes in menstrual flow and amenorrhea, thus, it is an ADR (adverse drug reaction) of the drug. If there is a delay in your periods than consult a gynecologist. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Munish Sood, Ayurveda Specialist