In the process of ovulation promotion, Letrozole is taken for 5 days is related to the pharmacological action of the drug and the level of sex hormones in the body. Letrozole is an aromatase inhibitor, which can inhibit the conversion of androgens to estrogens, reduce estrogen levels, and negatively feedback on the pituitary gland’s secretion of gonadotropins, thereby stimulating the growth and development of female follicles. Letrozole for ovulation promotion is recommended to be taken orally for 5 consecutive days starting from 3 to 5 days of menstruation. The reason for this medication is that during oral administration of Letrozole, a certain ratio of follicle-stimulating hormone and luteinizing hormone secreted by the pituitary gland is formed, and such an appropriate ratio is in line with the criteria for female ovulation. In the course of treatment, you should consult a professional physician and strictly follow the doctor’s instructions, if you change the dose of the drug privately or stop taking the drug may affect the effect of ovulation promotion and lead to the failure of the cycle of ovulation promotion.