Oestradiol (E2) explained: what the test shows across your cycle and in perimenopause.

Oestradiol, or E2, is the main oestrogen your ovaries make during your reproductive years. It rises and falls dramatically across a single cycle, from a low of roughly 100 to 200 pmol/L at the start of a period to a peak several times higher just before ovulation, so an oestradiol result only makes sense once you know the cycle day it was taken on.

Oestradiol, oestrogen and estrogen: the naming

Oestrogen is not one hormone but a family of three. Oestradiol (E2) is the strongest and by far the most important before menopause. Oestrone (E1) is weaker and becomes the main oestrogen after menopause, made mostly in fat tissue. Oestriol (E3) is produced in large amounts in pregnancy. When a doctor orders an "oestrogen test" for a woman with cycles, they almost always mean oestradiol.

The spelling is the other source of confusion. Australia and the United Kingdom write oestradiol and oestrogen; the United States writes estradiol and estrogen. They are the same hormones. Because so much online content is American, you will meet both spellings, and searches like "estradiol vs estrogen" are really asking about one member of a family and the family itself.

How E2 moves across a cycle, and why the day matters

Oestradiol is made by the follicle that is growing this month. At the start of your period there is no dominant follicle yet, so oestradiol is at its lowest. As FSH recruits a follicle and it grows, oestradiol climbs steadily, thickening the lining of the uterus and signalling back to the brain about the ovary's progress.

In the day or two before ovulation, oestradiol peaks. That peak is what triggers the LH surge and, with it, the release of the egg. Oestradiol then dips briefly, rises again to a smaller plateau through the luteal phase alongside progesterone, and falls away in the days before the next period.

That shape means the same woman can have a result of 150 pmol/L on day 3 and 1,200 pmol/L on day 13, both entirely normal. A "high" or "low" oestradiol is only high or low for the day it was taken. Baseline testing is done on day 2 to 5 for exactly this reason: it is the one window where the range is narrow and comparable between women. The FSH, LH and oestradiol article explains the feedback loop in more detail.

Typical ranges by phase

Australian laboratories report oestradiol in picomoles per litre (pmol/L). Overseas results are often in pg/mL; multiply pg/mL by about 3.67 to get pmol/L. The values below are typical for adult women not using hormonal contraception.

Phase	Typical adult range	What it usually means
Early follicular (day 2 to 5)	About 100 to 400 pmol/L	The baseline. Read with FSH: a raised FSH with a low oestradiol points one way, a raised FSH with a high oestradiol another.
Pre-ovulatory peak	Roughly 500 to 1,500 pmol/L	The mature follicle at full output, just before the LH surge.
Mid-luteal	Roughly 200 to 800 pmol/L	The second, smaller plateau from the corpus luteum, alongside raised progesterone.
After menopause	Usually below about 100 to 150 pmol/L	Consistently low, with a persistently high FSH.

Ranges vary by laboratory; your report shows the range your lab uses. Typical ranges on this page are drawn from Pathology Tests Explained (RCPA) and the sources listed below.

Low oestradiol: what it can reflect

A low early-cycle oestradiol on its own is normal; that is what the baseline looks like. Low oestradiol becomes meaningful when it goes with other findings, and the pattern of FSH alongside it tells your doctor which direction to look.

• Low oestradiol with a high FSH suggests the ovaries are responding less readily to the brain's signal. This is the pattern of the menopause transition, and, in a woman under 40, of primary ovarian insufficiency, which is investigated rather than assumed.
• Low oestradiol with a low or normal FSH suggests the signal from the brain is turned down, rather than the ovaries being unable to respond. Common reasons include significant stress, low body weight or under-eating, very high training loads, and raised prolactin. This is often called hypothalamic suppression, and it is usually reversible once the cause is addressed.
• Hormonal contraception suppresses your own oestradiol production by design. A low result on the pill mostly reflects the pill.
• Breastfeeding keeps oestradiol low for as long as feeding is frequent.

Signs that a woman's oestradiol has been low for a while can include periods that become light, infrequent or stop, vaginal dryness, hot flushes or night sweats, disturbed sleep, low mood, and, over the longer term, effects on bone. Each of those has other possible causes too, which is why a doctor puts the result and the symptoms together rather than reading one from the other.

Perimenopause: the moving target

In perimenopause, oestradiol does not decline in a tidy line. It swings. Some cycles the ovary over-produces and oestradiol runs higher than it did in your twenties; other cycles it barely gets going. FSH swings with it. That is why a single oestradiol reading cannot confirm or rule out perimenopause, and why Australasian Menopause Society guidance says that in women over 45 with typical symptoms, blood tests are not needed to make the assessment. The perimenopause blood test article covers when testing still earns its place.

High oestradiol: what it can reflect

A result that looks high is most often a timing question: a sample taken close to ovulation will naturally sit several times above the early-cycle range. Once timing is ruled out, a genuinely raised early-cycle oestradiol can reflect:

• Perimenopause, where erratic follicle activity can push oestradiol high in some cycles
• A rising FSH being masked. If a follicle starts growing early and makes oestradiol before day 3, it can pull FSH down into the normal range and hide a reserve picture the FSH alone would have shown. This is one reason the two are always measured together.
• An ovarian cyst that is producing hormone, which an ultrasound can look at
• Higher body weight, which raises oestrone and overall oestrogen exposure, though it rarely pushes early-cycle oestradiol above the range
• Prescribed hormone treatment, if your doctor has prescribed one; levels are then read against the treatment, not against the natural-cycle range

Persistently high oestradiol with heavy or prolonged bleeding, or with breast tenderness and bloating that does not settle, is worth a conversation with your doctor.

E2 in KnowLuna's fertility, hormone and perimenopause panels

Oestradiol is in every KnowLuna panel that looks at your cycle, always alongside FSH and LH so the three can be read as a set, and collected on day 2 to 5 where you have regular cycles. Which panel depends on your question.

• Thinking about fertility: the AMH and fertility panel reads oestradiol with FSH, LH, AMH, TSH and prolactin. Test-only $179, or $259 with a KnowLuna doctor to request and explain it.
• Irregular, heavy or changing cycles: the female hormone panel adds progesterone, testosterone, SHBG, prolactin, DHEA-S and cortisol. Test-only $139.
• Changes in your forties or fifties: the perimenopause and menopause panel reads oestradiol and FSH with thyroid and iron, because those so often mimic the transition.
• Symptoms a single snapshot has not explained: 28-day cycle mapping measures oestradiol and progesterone across eleven timed collections in one cycle, so your doctor sees the whole curve.

Collection is at accredited (NATA and RCPA) centres across Australia, and any abnormal result is followed up by an AHPRA-registered doctor. See the cycles and hormones stage for related tests, or FSH and LH levels for the other half of the picture.

Common questions

Sources and further reading

• Pathology Tests Explained (RCPA): oestradiol
• Healthdirect: oestrogen blood test
• Australasian Menopause Society: Diagnosing menopause (information sheet)
• Better Health Channel: menstrual cycle
• Jean Hailes for Women's Health: menopause

General information only, not medical advice. If your symptoms are severe or sudden, see a doctor promptly. This page does not replace a consultation with a doctor who knows your history; read our medical disclaimer.