Estriol and estradiol interact with estrogen receptors throughout the body. Estradiol is one of the primary estrogens present during the reproductive years, while estriol is another naturally occurring form of estrogen. Bi-Est Cream is applied to the skin as directed by the prescribing provider. The provider determines the estriol-to-estradiol ratio, formulation strength, application schedule, and follow-up plan based on the patient’s symptoms, health history, current medications, risk factors, and relevant laboratory findings when applicable. Although Bi-Est is sometimes considered for symptoms associated with menopause or hormonal changes, it is a compounded formulation and has not been evaluated by the FDA for safety or effectiveness.