Oestrogen is probably the most important hormone for a woman's body. It influences how we develop, our ability to reproduce, and even our mood. Oestrogen levels in our blood change often as our bodies change, so it's difficult to know exactly what's normal.
It's typical for oestrogen levels to fluctuate widely throughout a woman's menstrual cycle, and also during pregnancy and after menopause. So a "normal" level depends on what your body is experiencing right now; it can range from 50 to 400 picograms per millilitre (pg/ml).
According to Dr. Kelly Shanahan, an OB/GYN, normal levels of estradiol, the main type of oestrogen circulating in the body, are around 45 pg/ml during menstruation. During ovulation, levels rise to about 400 pg/ml, then fall quickly, and then rise again to about 250 pg/ml.
During pregnancy, oestrogen levels can be 100 times higher than normal. Levels also fluctuate during pregnancy in order to increase blood flow to the uterus and stimulate lactation postpartum. After birth, levels decrease rapidly.
After menopause, women who are not on hormone replacement therapy usually experience oestrogen levels around 10 to 20 mg/pl. However, the level of oestrogen required to maintain healthy bones is 40 to 50 mg/pl, so many doctors prescribe hormone therapy for post-menopausal women. Some women, however, need even higher levels to avoid hot flushes.
Abnormal Estrogen Levels
Oestrogen levels that are too high or too low can result in many health problems for women. High levels have been associated with PMS, polycystic ovarian syndrome, amenorrhoea (absence of menstruation), and breast and ovarian cancer. Low levels have been associated with osteoporosis, miscarriage and birth defects.