what is what is serum estriol level
Guide. An estrogen test measures the level of the most important estrogen hormones (estradiol, estriol, and estrone) in a blood or urine sample. 1  Estradiol is the most commonly measured type of estrogen for nonpregnant women.2  The amount of estradiol in a woman's blood varies throughout her menstrual cycle. Estradiol is the most commonly measured type of estrogen for nonpregnant women. 2  The amount of estradiol in a woman's blood varies throughout her menstrual cycle. 3  After menopause, estradiol production drops to a very low but constant level. 4  Estriol levels usually are only measured during pregnancy.