No estrogen on bloodwork but having cycles?

Estrogen levels...: ...vary depending on where in the cycle you are. If the Estradiol (ovarian estrogen) is really undetectable, then it could be timing dependent, or you could be having cycles due to another source of estrogen (pills, patches, fat cells, etc). Furthermore you could be having postmeopausal bleeding which is a risk for cancer. see a gynecologist!