Dienogestrel is primarily used in hormonal contraceptives, including birth control pills and intrauterine devices (IUDs), to prevent pregnancy. It works by inhibiting ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining to prevent implantation. Additionally, it is prescribed for managing endometriosis, reducing pelvic pain, and controlling abnormal uterine bleeding. In some cases, it is also used in hormone replacement therapy (HRT) to alleviate symptoms of menopause. Its anti-androgenic properties make it effective in treating conditions like acne and hirsutism in women.