Estradiol pg/mL to pmol/L Converter

Estradiol in two units: the short answer

To convert estradiol (E2) from pg/mL to pmol/L, multiply by 3.671. To convert pmol/L back to pg/mL, divide by 3.671 (or multiply by 0.2724). An estradiol of 50 pg/mL is therefore about 184 pmol/L, and 600 pmol/L is about 163 pg/mL. Because pg/mL equals ng/L, results in ng/L can be read as pg/mL. The converter above handles both directions and shows typical ranges across the menstrual cycle, after menopause and in men.

Estradiol is a hormone whose "normal" value depends on who is being tested and when: a level that is expected in the middle of a cycle would be very high after menopause, and a level that is normal in a man would be low for a woman in the follicular phase. Conversion mistakes add a further layer of confusion, especially in fertility treatment, menopause care and gender-affirming hormone therapy, where target ranges are often quoted in only one unit. This guide explains the conversion, what estradiol measures, how levels change through life, and the factors that affect the test.

What estradiol is

Estradiol (17β-estradiol, E2) is the most potent and most abundant oestrogen in women of reproductive age. It is made mainly by the developing follicles in the ovaries, with smaller amounts made in fat tissue, the adrenal glands and, in men, the testes and by conversion of testosterone through the aromatase enzyme. Estradiol:

• drives the growth of the uterine lining in the first half of the menstrual cycle
• triggers the surge of luteinizing hormone (LH) that causes ovulation
• supports breast development and the development of female secondary sexual characteristics
• protects bone density in both women and men
• has effects on the brain, blood vessels, skin and lipid metabolism

Two other oestrogens are sometimes measured: estrone (E1), the main oestrogen after menopause, and estriol (E3), which is produced in large amounts by the placenta during pregnancy. They are different tests with different ranges.

pg/mL and pmol/L explained

• pg/mL (picograms per milliliter) – the usual unit in the US; identical to ng/L.
• pmol/L (picomoles per liter) – the SI unit, used in the UK, Europe, Australia and many other countries.

Why the factor is 3.671

Estradiol's molar mass is 272.4 g/mol. One picomole weighs 272.4 pg. A concentration of 1 pg/mL is 1,000 pg per liter, which is 1,000 ÷ 272.4 = 3.671 pmol/L. Conversely, 1 pmol/L = 0.2724 pg/mL.

How to convert estradiol step by step

1. Check the unit on the report: pg/mL, ng/L or pmol/L.
2. For pg/mL (or ng/L) to pmol/L, multiply by 3.671.
3. For pmol/L to pg/mL, divide by 3.671.
4. Round pmol/L to whole numbers, and pg/mL to whole numbers above 10 or to one decimal place below 10.

Worked examples

• 20 pg/mL × 3.671 = 73 pmol/L – a typical value after menopause or in men.
• 50 pg/mL × 3.671 = 184 pmol/L – typical of the early follicular phase.
• 100 pg/mL × 3.671 = 367 pmol/L – a common target for oestrogen therapy.
• 300 pg/mL × 3.671 = 1,101 pmol/L – typical of the pre-ovulatory peak.
• 2,000 pg/mL × 3.671 = 7,342 pmol/L – a level that may be seen during IVF stimulation.
• 150 pmol/L ÷ 3.671 = 41 pg/mL.
• 800 pmol/L ÷ 3.671 = 218 pg/mL.

Mental shortcut

Multiply pg/mL by 3.7, or divide pmol/L by 3.7. For 60 pg/mL: 60 × 3.7 = 222 pmol/L (exact: 220).

Estradiol conversion chart

Normal estradiol ranges

The ranges above are typical values; each laboratory sets its own, and they vary noticeably with assay type. The pattern, though, is consistent.

Across the menstrual cycle

Estradiol rises steadily as a dominant follicle grows, peaks a day or so before the LH surge, falls briefly at ovulation and then rises again in the luteal phase as the corpus luteum produces both estradiol and progesterone. If pregnancy does not occur, both hormones fall and menstruation follows.

Puberty and childhood

Before puberty, estradiol is very low – often below 10–15 pg/mL (37–55 pmol/L) – and sensitive assays are needed to measure it. Rising levels mark the onset of puberty. In children, LC-MS/MS or ultra-sensitive assays are preferred, because standard immunoassays are unreliable at these low concentrations.

Pregnancy

Estradiol rises progressively throughout pregnancy, reaching several thousand to tens of thousands of pg/mL by the third trimester as the placenta takes over production. Estradiol is rarely measured to monitor a normal pregnancy.

Menopause

After menopause, the ovaries stop producing significant estradiol, and levels fall to below about 30 pg/mL (110 pmol/L), often below 20 pg/mL. Most remaining oestrogen is estrone made in fat tissue. In perimenopause, estradiol can swing widely from very low to higher than in younger women, so single measurements are of limited use. Guidelines, including NICE in the UK, advise diagnosing menopause in women over 45 based on symptoms and periods rather than blood tests.

Estradiol in clinical practice

Fertility assessment and IVF

A day 2–5 estradiol is often measured with follicle-stimulating hormone (FSH). A raised early-follicular estradiol (above about 60–80 pg/mL, 220–294 pmol/L) can falsely lower FSH and may indicate reduced ovarian reserve. During ovarian stimulation for IVF, estradiol is measured repeatedly to track follicle growth: each mature follicle typically contributes roughly 200–300 pg/mL (730–1,100 pmol/L). Very high levels, sometimes above 3,000–4,000 pg/mL (11,000–14,700 pmol/L), raise concern about ovarian hyperstimulation syndrome. Because IVF protocols are often written in pg/mL, patients receiving results in pmol/L frequently need to convert them.

Menopausal hormone therapy

Blood levels are not routinely needed to monitor HRT, because dosing is guided by symptom relief. When measured – for example if symptoms persist despite a transdermal preparation – typical levels on standard-dose therapy are often around 50–100 pg/mL (184–367 pmol/L). Oral oestrogens produce relatively more estrone than estradiol, so estradiol levels can underestimate oral oestrogen exposure.

Gender-affirming hormone therapy

For transgender women and transfeminine people taking estradiol, the Endocrine Society guideline suggests maintaining estradiol at 100–200 pg/mL (367–734 pmol/L) and testosterone at the female range (below about 50 ng/dL, 1.7 nmol/L). UK and other guidelines use similar targets expressed in pmol/L. Timing of the sample relative to the dose (for example mid-way between injections or several hours after a patch change) strongly affects the result, so local guidance on timing should be followed.

Men

In men, estradiol is measured when there is breast enlargement (gynecomastia), symptoms of hypogonadism, or during testosterone therapy. Levels above about 40–50 pg/mL (147–184 pmol/L) in men can occur with obesity, liver disease, testosterone therapy, aromatase-producing tumours or certain medicines. Low estradiol in men contributes to bone loss in hypogonadism.

Low estradiol

In premenopausal women, a persistently low estradiol together with absent or infrequent periods usually reflects reduced signalling from the brain or reduced function of the ovaries:

• Hypothalamic amenorrhoea – caused by low energy availability, excessive exercise, weight loss, eating disorders or major stress. LH and FSH are low or normal.
• Premature ovarian insufficiency (POI) – loss of ovarian function before 40. FSH is raised (above about 25 IU/L on two occasions, four to six weeks apart, under ESHRE guidance) and estradiol is low.
• Pituitary disorders – including high prolactin, which suppresses the reproductive axis.
• Medicines – GnRH analogues, aromatase inhibitors, and long-acting progestogen contraceptives such as the injection.

Prolonged low estradiol matters because it leads to bone loss and may increase cardiovascular risk. Women with POI are usually advised to take hormone replacement until at least the average age of natural menopause (about 51), unless there is a reason not to.

High estradiol in women

A high estradiol outside the expected cycle pattern can be caused by:

• a functional ovarian cyst producing oestrogen
• ovarian stimulation for fertility treatment
• obesity, which increases peripheral production
• liver disease, which reduces oestrogen breakdown
• rarely, oestrogen-secreting tumours of the ovary or adrenal gland
• oestrogen therapy with higher doses or a sample taken soon after a dose

Postmenopausal bleeding should always be assessed, whatever the estradiol level, because it can be a sign of endometrial problems.

Following estradiol through a cycle: an example

A woman tracking a cycle has results from a UK laboratory on day 3 (150 pmol/L), day 12 (1,250 pmol/L) and day 21 (520 pmol/L), and wants to compare them with a US fertility guide written in pg/mL. Converted, these are about 41, 341 and 142 pg/mL. The pattern – low early, a clear pre-ovulatory peak and a moderate luteal level – is consistent with an ovulatory cycle. Ovulation is better confirmed with a mid-luteal progesterone measurement, which is the test most clinics use for that purpose.

Estradiol and bone health

Estradiol is a key regulator of bone remodelling in both sexes. It slows the activity of osteoclasts, the cells that break down bone. When estradiol falls – at menopause, in premature ovarian insufficiency, with prolonged hypothalamic amenorrhoea, during treatment with aromatase inhibitors or GnRH analogues, and in men with untreated hypogonadism – bone loss accelerates. Women lose bone fastest in the first five to ten years after menopause, sometimes 2–3% a year.

Studies in older men have found that estradiol below about 15–20 pg/mL (55–73 pmol/L) is associated with lower bone density and higher fracture risk, often more strongly than testosterone. This is one reason testosterone therapy, part of which is converted to estradiol, supports bone in hypogonadal men. Anyone with prolonged low estradiol should discuss bone density assessment with their clinician.

What affects estradiol results

• Cycle day – the single largest influence in premenopausal women. Always note the cycle day when interpreting a result.
• Assay method – standard immunoassays are less accurate at low concentrations (men, children, postmenopausal women, women on aromatase inhibitors). LC-MS/MS is preferred in these settings, and results can differ by 20–50% between methods at low levels.
• Cross-reactivity – some immunoassays cross-react with other steroids or drugs, including fulvestrant, which can give falsely high estradiol results.
• Hormonal contraceptives – combined pills suppress the ovaries and lower natural estradiol; the synthetic ethinylestradiol in many pills is usually not detected by estradiol assays.
• Body fat – adipose tissue converts androgens to oestrogens, raising levels after menopause and in men.
• Biotin supplements can interfere with some immunoassays.
• Medicines – aromatase inhibitors, GnRH analogues and some antiepileptic drugs lower estradiol; oestrogen therapy and clomiphene raise it.

Estradiol in breast cancer treatment

Many breast cancers are driven by oestrogen, and treatment often aims to lower it. In postmenopausal women, aromatase inhibitors such as anastrozole, letrozole and exemestane block the conversion of androgens to oestrogens in fat and other tissues. In premenopausal women, ovarian function suppression with GnRH analogues may be combined with these medicines. Estradiol testing is sometimes used to confirm that suppression is adequate, and here method matters greatly: the target levels are very low, often below about 10–20 pg/mL (37–73 pmol/L), which standard immunoassays cannot measure accurately. Guidelines therefore recommend sensitive LC-MS/MS assays for this purpose. Fulvestrant, another breast cancer medicine, can cause falsely high estradiol results on some immunoassays, which could wrongly suggest that the ovaries are active.

When to see a doctor

See a doctor if you have absent, very irregular or very heavy periods, hot flushes and other menopausal symptoms before the age of 40 (a possible sign of premature ovarian insufficiency), difficulty conceiving, unexpected breast development in a man or a child, or early signs of puberty in a child. People on oestrogen therapy should seek urgent care for signs of a blood clot – a swollen painful calf, chest pain or sudden breathlessness – regardless of their estradiol level.