Reading FSH and estradiol on a lab report gets complicated fast when you’ve lived in more than one country. A number that looked alarming on a Seoul lab slip turns out to be unremarkable against the range your doctor at home used. Or the reverse.
Before anything else: this is about understanding what’s printed on the page, not about diagnosing yourself. Interpretation belongs in a consultation. What follows is meant to make that consultation more useful.
The four values you’re likely to see
A hormone panel around this stage of life usually reports some combination of four things.
- FSH — follicle-stimulating hormone, released by the pituitary to stimulate the ovaries. It rises as ovarian function declines.
- E2 (estradiol) — the principal estrogen produced by the ovaries.
- LH — luteinizing hormone, also pituitary in origin.
- AMH — anti-Müllerian hormone, reflecting remaining follicle reserve.
Not every panel includes all four, and in some healthcare systems most of them won’t be ordered at all. If your report is shorter than you expected, that usually reflects local practice rather than an oversight.
Units: where cross-border comparison breaks
This is the practical problem nobody warns you about.
FSH and LH are reported in either mIU/mL or IU/L. These are numerically identical — one thousand millilitres make a litre, and one thousand milli-international-units make an international unit, so the two cancel out. A value of 30 mIU/mL and a value of 30 IU/L are the same result. No conversion needed.
Estradiol is where it goes wrong. It’s reported as pg/mL in some regions and pmol/L in others — and these are *not* interchangeable. One is a mass concentration, the other a molar concentration, so converting requires the molecular weight of estradiol, roughly 272 daltons[1].
The working figure: 1 pg/mL ≈ 3.67 pmol/L[1].
That means 40 pg/mL and 147 pmol/L describe the same blood. Read one against a reference range built for the other and you’ll be off by nearly fourfold — enough to turn an ordinary result into a frightening one, or to hide a meaningful one.
One more that trips people up: 1 pg/mL is exactly 1 ng/L. If your report uses ng/L, no conversion is required.
Broadly, pg/mL predominates in the United States while pmol/L is standard across much of Europe, the UK, Canada and Australia[1]. Rather than assume, look at the unit printed on your own report — it’s usually in small type beside the value.
Reference ranges belong to the lab, not to you
The second reason numbers don’t line up: reference intervals aren’t universal. They vary by laboratory and by the assay platform used[1].
This isn’t sloppiness. Different immunoassays measure the same molecule with different antibodies and calibration, so each laboratory establishes intervals appropriate to its own method. Two labs can report the same sample within their respective normal ranges while printing different boundaries.
The practical rule is simple, and it holds everywhere: compare your value against the range printed on your own report, not against a chart found online — including any chart in this article.
Why the range is split into rows
On many reports the estradiol reference range isn’t one line but several — follicular phase, mid-cycle, luteal phase, postmenopausal.
Estrogen output changes substantially across a normal menstrual cycle, so a single interval would be meaningless. As an illustration of the scale involved, follicular-phase values are often cited around 30–100 pg/mL, mid-cycle peaks considerably higher, and postmenopausal values well below that[1].
Which creates an awkward problem during the transition. Cycles become irregular, so which row applies to you is itself uncertain. Reading your value against a phase you may or may not be in is guesswork dressed up as measurement.
This is one reason staging frameworks treat menstrual cycle change as the primary criterion and hormone values as supporting evidence[5].
A single draw is a snapshot of a moving target
Even with the right units and the right range, one measurement carries limited weight in this particular window.
FSH is elevated but erratic in the early transition, and climbs above 25 IU/L by the late transition[2]. Between those points it moves around. Estradiol is less stable still. Guidance notes that FSH fluctuates substantially over short periods and doesn’t correlate with the severity or duration of symptoms[3].
This is why clinicians often repeat testing at an interval rather than acting on one value, and why a result inside the reference range doesn’t rule out that the transition is underway.
Two things worth mentioning before the blood draw
Hormonal contraception affects the result. If you’re using combined estrogen-progestogen contraception or high-dose progestogen, FSH readings are altered and shouldn’t be relied on for this purpose[3]. Say so at the appointment.
Thyroid symptoms overlap considerably. Fatigue, weight change, anxiety, low mood, constipation or looser stools, cycle irregularity, temperature sensitivity — these appear in both pictures, and thyroid disorders are commonly identified in women around this age. Korean research has argued that thyroid function testing warrants consideration in transitional women presenting with menopausal complaints, precisely because the presentations are so similar[4].
So a hormone panel that comes back unremarkable isn’t necessarily the end of the enquiry. It may point elsewhere.
If you carry records between countries
A short checklist for anyone whose medical history is spread across more than one system.
- Photograph the whole page, not just the number. The unit and the reference interval sit in the surrounding text and are the parts that make the value interpretable elsewhere.
- Note the date and, if you know it, the day of your cycle. Both change how the result reads.
- Keep the assay name if it’s printed. It explains discrepancies between labs.
- Keep your own cycle and symptom notes alongside. Where guidance leans on symptoms and cycle change rather than laboratory values[3], that record is the more portable document.
Closing
A lab report isn’t a verdict. It’s one measurement, taken on one day, on a scale set by one laboratory, using one assay.
The thing I found genuinely useful to understand was that mismatched numbers usually aren’t a sign that something went wrong. Different units, different reference intervals and a hormone that moves on its own account for most of it. Knowing that saves a fair amount of unnecessary alarm — and makes the appointment where it actually gets interpreted a far more productive one.
At a Glance
- FSH: mIU/mL and IU/L are numerically identical — no conversion needed
- Estradiol: pg/mL and pmol/L are not interchangeable — roughly 1 pg/mL ≈ 3.67 pmol/L
- 1 pg/mL equals exactly 1 ng/L
- Reference intervals vary by laboratory and assay — compare against the range on your own report
- Estradiol ranges are split by cycle phase, which becomes ambiguous once cycles turn irregular
- FSH exceeds 25 IU/L in the late transition but fluctuates considerably before that
- Hormonal contraception alters FSH results; thyroid conditions mimic menopausal symptoms
※ This article explains how laboratory reports are structured and is for general information only. It does not replace medical diagnosis, interpretation or treatment. Reference ranges and their interpretation depend on your individual circumstances, the timing of the sample and the laboratory’s method. Please have your results interpreted by a clinician, and do not adjust medication or supplements on the basis of a value you have read yourself.
References
- UNITSLAB, “Estradiol (E2) unit conversion — pmol/L, pg/mL, ng/L”, https://unitslab.com/node/113
- StatPearls, “Menopause”, NCBI Bookshelf, https://www.ncbi.nlm.nih.gov/books/NBK507826/
- NICE, “Menopause: identification and management (NG23)” — Recommendations, https://www.nice.org.uk/guidance/ng23/chapter/recommendations
- 「폐경 증상을 호소하는 폐경 이행기 여성에서 갑상선 감별 진단의 필요성」, Journal of the Korean Society of Menopause, https://synapse.koreamed.org/upload/synapsedata/pdfdata/0165jksm/jksm-18-174.pdf
- American Society for Reproductive Medicine, “Executive summary of the Stages of Reproductive Aging Workshop +10”, https://www.asrm.org/practice-guidance/practice-committee-documents/executive-summary-of-the-stages-of-reproductive-aging-workshopd10-addressing-the-unfinished-agenda-of-staging-reproductive-aging-2012/