It is considered normal for women with regular menstruation to have occasional early onset of menstruation after taking ovulation injections, and the menstruation is not more than 7 days early. If a woman frequently experiences early onset of menstruation, more than 7 days in advance, it is not normal, which is considered to be due to diseases such as endometriosis. Ovulation stimulation injection contains luteinizing hormone, follicle-stimulating hormone and other two gonadotropins, which have the effect of promoting follicle development and ovulation, but will not have an effect on the time of menstruation. If a woman with regular menstruation occasionally experiences early menstruation and the period is not more than 7 days early, it is considered to be caused by mental stress or anxiety, irregular work and rest, etc. This is a normal phenomenon that does not require treatment. If a woman’s menstrual period is often early after taking ovulation injections, and the period is more than 7 days early, it is generally an abnormal phenomenon. This may be caused by endometriosis, adenomyosis, luteal insufficiency and other factors. Ovulation injections usually do not affect the timing of menstruation and do not cause early menstruation. If a woman experiences early menstruation after taking ovulation injections, she needs to seek medical attention, and the doctor will determine whether it is normal or not, depending on the cause of the early menstruation.