If you take Nea CR-10 (which contains norethisterone) to delay your period, it is usually recommended to start the tablet 3–4 days before your expected period. It works by keeping progesterone levels high, which prevents the uterine lining from shedding, so your period is delayed. After stopping the tablet, your period generally starts within 2–3 days. The exact timing may vary slightly depending on individual health, diet, and lifestyle.