Nornal menstural cycle can be postponed if it is really required Anita & it it should not be attempted very often. Because the drug norethisterone is a female hormone progesterone. It is a synthetic progestin with weak androgenic & estrogenic action. Progesterone results in secretary changes in uterus & leads to withdrawal bleeding and this property is utilised therapeutically to induce breakthrough bleeding or period. Progesterone preparation Norehisterone is given as 5mg tab twice daily given three days before the expected period & continued as long as required. Period starts within 2 to 3 days of stopping the tab. Mensturation occurs due to sudden fall in progesterone level resulting in breakthrough bleeding. But in reproductive age groups, if this is practised freequently progesterone can disrupt the menstural cycles & can sometimes lead to ammenorrhea (complete arrest of menstural cycle). Though rare with oral preparations & only freequent with injectable preparation this side effect should be remembered if you are planning for future pregnancy. To prepone your next period take Norethisterone 5mg twice a day exactly from the 23th day (from the 1st day of your period) for three days. Good luck & happy holidays Anita.