Estradiol

Blood test

Also known as: E2, 17β-estradiol

There is no single guideline cutoff for estradiol. The result is read against age- and sex-specific ranges with a clinician.

Guidelines advise against using estradiol to diagnose menopause in women aged 45 or over (NICE, 2015).

Estradiol is the main estrogen in both women and men. Before menopause, the ovaries make most of it and levels swing widely across the cycle. In men and after menopause, levels are low and come mostly from other hormones converted in fat and other tissues.

What it tells you

The test measures total estradiol: the hormone bound to proteins and the free hormone together.
Estradiol matters in men too. In a trial of 400 men, losing estrogen mainly drove fat gain, and losing both estrogen and testosterone lowered sexual function.
Many standard immunoassays cannot measure the low levels found in men, children and women after menopause. Mass spectrometry methods do better, though they also struggle at very low levels.
Guidelines use estradiol narrowly. In women aged 45 or over, menopause is diagnosed from symptoms, without lab tests.
A 2022 menopause society statement says blood hormone tests are rarely needed to adjust hormone therapy, and saliva and urine tests are unreliable.
The Endocrine Society's monitoring plan for men on testosterone therapy does not include estradiol.

What can throw it off

Lab method matters most. Many direct immunoassays cannot measure below 30 to 100 pg/mL, and some substances can make them read up to 10 times too high. Results from different methods cannot be swapped.
Before menopause, levels swing widely across the cycle and from one cycle to the next. One result means little without the cycle day.
During the menopause transition, hormones fluctuate. That is why estradiol is not used to diagnose menopause at 45 or over.
Biotin supplements can make some estradiol immunoassays read falsely high.
Fulvestrant, a breast cancer drug, can make estradiol immunoassays read falsely high. Mass spectrometry is recommended for people taking it.
On estrogen pills, more of the hormone is turned into estrone, a weaker estrogen. Estradiol alone then under-reads total estrogen exposure.
Aromatase inhibitors, drugs that block estrogen production, lower it. On immunoassays, very low results in people taking them are most likely errors.
Levels vary over the day. No guideline sets a fasting rule.

Evidence

Diagnosing menopause at 45 or over

Animal and lab studies onlyCEBM Level 5

The UK guideline says to diagnose menopause from symptoms at this age and not to use estradiol. Hormones swing during the transition, and estradiol varies widely even between one woman's cycles. No accuracy study was found that supports the test for this use.

Understanding estradiol's role in men

Strong human evidenceCEBM Level 1b

In a trial, 400 healthy men aged 20 to 50 had their own hormones switched off with medicine and partly replaced. Estrogen loss mainly drove fat gain. Estrogen and testosterone loss both lowered sexual function. These were short-term results in healthy men, not men on long-term testosterone therapy.

Adjusting menopause hormone therapy

Animal and lab studies onlyCEBM Level 5

A 2022 menopause society statement says blood hormone tests are rarely needed for dosing, and saliva and urine tests are unreliable. Dose is guided by symptoms.

Limits

Lab method is everything at low levels. An immunoassay result in a man or in a woman after menopause may simply be wrong, so results from different methods cannot be compared.
One result before menopause is hard to read without the cycle day, and it varies from cycle to cycle.
There is no outcome-based healthy range for estradiol in men or women.
It measures total estradiol only. It does not show the free fraction, which SHBG changes.
On estrogen pills, it misses estrone, which carries much of the estrogen effect.

References

Reviewed by Shubham Gupta, MD — Founder & President · November 5, 2026

This page is for education only. It is not medical advice. Decisions about any treatment belong with a physician who knows your history.