It is normal to have a period during the down regulation, but it is normal to have another down regulation in the next menstrual cycle. The main purpose of down regulation is to suppress the hormone levels in the body through medication, which can reduce the rate of follicle development and effectively prolong the development time of follicles. This can increase the number of mature follicles at the same time, thus achieving the goal of collecting more mature follicles. However, because each person’s sensitivity to the medication varies, it is not always possible to be successful at once when performing the medication to lower the level. When the follicles in the body are not under control and ovulation still occurs on its own, the woman will have her period, which is a common occurrence during the down regulation. Therefore, when menstruation occurs, it means that the regimen has failed and the regimen can be reintroduced in the next menstrual cycle.