What is Estriol(E3)?

The least potent of the estrogens, Estriol (E3) levels are traditionally used clinically to gauge the viability of pregnancies. In the context of this profile, estriol is least likely to be associated with high-estrogen problems (e.g. breast cancer), and is generally viewed as a “protective” estrogen. Conversion of 16alpha-hydroxyestrone to estriol is important to consider. If one is taking a “Bi-Est” or “Tri-Est” preparation, an elevated estriol is not unusual.

Abnormal levels:

Doctors usually test E3 during pregnancy, when it temporarily becomes the main estrogen. Abnormal levels of estriol may be a sign of problems with the baby’s health — but you’d get a lot more tests to find out for sure. You might need several tests to track changes in your estrogen levels over time.


Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

The information on is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.

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