Estradiol's two rises across the cycle
Estradiol (E2) is the principal estrogen tracked across the menstrual cycle, and it has a distinctive double-humped pattern. During the follicular phase, growing ovarian follicles raise estradiol steadily until it peaks just before ovulation. That peak helps trigger the luteinizing hormone surge that releases the egg.
After ovulation, estradiol briefly dips, then rises a second time during the luteal phase as the corpus luteum produces it alongside progesterone. If pregnancy does not occur, the corpus luteum regresses and estradiol falls again, marking the end of the cycle.
Why exact day numbers vary
Charts often place the estradiol peak around day 13 of a 28-day cycle, but cycle length and the timing of ovulation differ widely between people and even between cycles for one person. The pattern of two rises is reliable; the precise calendar day is an average, not a rule.
This is general educational information, not medical advice. Cycle tracking for contraception, fertility, or symptom concerns should be guided by a qualified professional.