Period Delay Medical Information Women who have regular periods, sometimes want to utilize period delay treatments short term when going on a vacation or special event. Period delay medication cause a change in hormones which causes menstrual cycles to be delay. Period Delay medication does not prevent Pregnancy or STDs/HIV. Norethisterone 5mg tablets can be taken to delay periods. The medication should be taken three days before the onset of period, for up to 20 days. This will delay the period for the desired time and Period should start two to four days after the pills is stopped. The balance of hormones changes during the menstrual cycle thus will be delayed. This medication is not a contraceptive and will not prevent pregnancy. Side effects include bloating, breast tenderness, and loss of libido. Other less common effects are fluid retention which can worsen if the person has a history of migraine, epilepsy, hypertension and asthma. The risk of developing Venous Thromboembolism (VTE) is also increased while on the medication.