Norethisterone 5mg tablets work by mimicking the effects of the natural hormone, progesterone.Through your menstrual cycle levels of progesterone will naturally rise and fall.? Taking norethisterone tablets a few days before your period is due to start can temporarily stop the shedding of the womb lining, which helps to stop/delay your period.Once you stop taking Norethisterone, your progesterone levels will return to normal and your next period will usually start again within 2-3 days.Norethisterone should only be used occasionally to delay a period.? If you find that you need to use this regularly then please sAllschoolabs with your GP as a low-dose hormonal contraceptive (like the pill)?might be more suitable for controlling frequent or heavy uncomfortable periods.??Please note: this medicine is not a contraceptive.