The Who, What, Where, When and Sometimes, Why.

Blood Estrogen Levels

Estrogens are natural hormones. They are important in sexual development and other body functions.

Before menopause, most estrogens are produced in the ovaries. After menopause, the ovaries no longer produce much estrogen and estrogens mainly come from fat tissue.

After menopause, higher amounts of estrogen in the blood are linked to an increased risk of breast cancer in women [18].

Researchers are studying a possible link to breast cancer before menopause.


For a summary of research studies on estrogen levels and the risk of breast cancer, visit the Breast Cancer Research Studies section.

Blood estrogen levels and breast cancer after menopause

Studies show postmenopausal women with higher blood levels of the estrogen estradiol have an increased risk of breast cancer [18,64-66].

A pooled analysis of data from 9 studies found the risk of breast cancer was twice as high among women with higher levels of estradiol compared to women with lower levels [18].

Health care providers don’t use blood estrogen levels to assess breast cancer risk. However, this measure may be useful in the future [69-71].

Certain factors that affect estrogen levels in the body are linked to an increased risk of breast cancer.

Body weight is an important example. Estrogen is produced in fat tissue. In general, more weight means more fat tissue and higher estrogen levels in postmenopausal women. This likely explains, at least in part, the increased breast cancer risk in women who are heavy after menopause.

Learn more about body weight and breast cancer risk

Blood estrogen levels and breast cancer before menopause

A pooled analysis of data from 7 studies found women with higher blood estrogen levels may have a modestly increased risk of breast cancer before menopause [67].

Studies in premenopausal women are challenging because estrogen levels vary over the menstrual cycle. For example, in the early phase of the menstrual cycle (follicular phase), estrogen levels are much lower than in the late phase (luteal phase).

Factors that affect blood estrogen levels

Blood estrogen levels are affected by many factors. Some of these are under your control.

Factors linked to lower estrogen levels in women include [18]:

These steps may be linked to a decreased risk of breast cancer and other chronic diseases.

Updated 03/07/22