Estriol (E3) Blood Test
An estriol test measures E3, one of the three main estrogens the body makes. Estriol is present in small amounts most of the time and becomes far more prominent during pregnancy, when the placenta produces it.
About this test
The body makes three principal estrogens: estradiol, estrone, and estriol. Estradiol is the most active form during the reproductive years, estrone becomes relatively more prominent after menopause, and estriol is the form most associated with pregnancy. Outside of pregnancy, estriol circulates at low levels; during pregnancy the placenta produces it in much larger quantities, drawing on precursors supplied by the developing baby's adrenal glands and liver.
That production pathway is what makes estriol interesting to clinicians. Because it depends on both the placenta and the fetus, it is one of the markers used in certain prenatal evaluations, always as part of a set rather than on its own. Outside pregnancy, it occasionally appears in a broader estrogen review when a clinician wants to see how the three forms compare.
The sample is a routine blood draw at a Quest patient service center. You order the test online and pay the cash price shown on this page. The physician's order is arranged for you, so no separate doctor's visit is needed first, and no insurance is billed at any stage.
Who commonly orders it
Most people who look into estriol are doing so during pregnancy, usually because a clinician has included it in a group of prenatal markers evaluated together. In that setting, estriol contributes one piece to a combined result that an obstetric clinician interprets — it is never read as an answer by itself, and the timing of the sample within pregnancy matters a great deal to what it means.
A smaller number of people encounter estriol outside pregnancy, generally as part of a fuller look at estrogen forms with a clinician who is exploring hormone balance. Because estradiol is the more informative marker for most non-pregnancy questions, estriol is usually an addition to that picture rather than the starting point.
How estriol differs from estradiol and estrone
Estradiol is the most biologically active estrogen and the one most often measured in fertility, cycle, and menopause conversations. Estrone is the form that becomes relatively more prominent after menopause. Estriol is weaker in activity and normally present in modest amounts, rising substantially only in pregnancy.
Because the three behave differently, they are not interchangeable on a lab order. Ordering the wrong one produces a result that does not address the question being asked, so it is worth confirming with a clinician which estrogen fits your situation before testing.
Estriol in pregnancy
During pregnancy, estriol production reflects a shared pathway between the placenta and the developing baby. That is why it is included in certain prenatal marker panels, where it is evaluated together with other substances and with gestational dating rather than assessed individually.
Because pregnancy dating drives interpretation, an estriol measurement without an accurate gestational age is difficult to make sense of. An obstetric clinician reviews the full set of results in that context and explains what, if anything, warrants follow-up.
Preparation and collection
No fasting is typically needed for estriol, though a clinician may give specific instructions depending on what else is being collected. Mention any hormone medication, hormonal contraception, or supplement you take, since these can influence estrogen measurements generally.
The draw itself takes a few minutes at a patient service center, and most locations accept walk-ins during open hours. Your report is delivered to you securely once the laboratory has finished.
Ordering and pricing
The cash price shown beside the order button covers the laboratory work and the physician's order. There is no insurance claim to file, no referral to track down, and no membership. If you are pregnant and being followed by an obstetric clinician, it is sensible to coordinate any hormone testing with them so results land in the right hands.
Your results
Results will be emailed securely to you as a PDF.
One-time price · physician order included · no insurance needed
Prefer a fuller panel?
A curated bundle groups this test with the markers clinicians most often review alongside it — often better value than single tests.
Frequently asked questions
What is estriol?+–
Estriol, or E3, is one of the three main estrogens. It circulates at low levels most of the time and is produced in much larger amounts by the placenta during pregnancy.
How is estriol different from estradiol?+–
Estradiol is the most active estrogen and the one usually measured for cycle, fertility, and menopause questions. Estriol is a weaker estrogen that becomes prominent mainly in pregnancy, so the two are ordered for different reasons.
How much does an estriol test cost?+–
The cash price is displayed next to the order button on this page and includes the physician's order. No insurance is billed and no separate visit fee applies.
Do I need to fast before this test?+–
Fasting is not usually required. Follow any preparation instructions your ordering clinician provides, especially if other tests are collected at the same appointment.
Can an estriol result stand on its own?+–
Not in most situations. In pregnancy it is evaluated as part of a group of markers with accurate gestational dating, and outside pregnancy it is generally reviewed alongside other estrogens by a clinician.