I am going abroad at the end of August for 10 days, as my menstral cycle is very irregular after being on the pill I asked my gp if there was anything she could prescribe me to make sure I didn't have my period while on holiday, she prescribed me Norethisterone which she told me to take for two weeks making sure there was a week gap between finishing the 2 week cycle of tablets and the start of my holiday where I would have my period, but it says that you have to take norethisterone 3 days before your cycle to work effectively, does anyone know how effective Norethisterone will be how I have been told to take it? Thanks:)