Oestrogens . Patient guide
Follicle Stimulating Hormone (FSH)
What is FSH
Follicle Stimulating Hormone (FSH) is a pituitary hormone that drives ovarian follicle development in women and testicular sperm production in men. In women, FSH is the single most useful marker for confirming the menopause transition.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in IU/L. Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Cycling women, early follicular (days 2-5) | 3.5 to 12.5 | IU/L; the standard timing for baseline FSH |
| Cycling women, ovulation peak | 4.7 to 21.5 | |
| Cycling women, luteal phase | 1.7 to 7.7 | |
| Perimenopausal (variable) | 10 to 40 | often fluctuating widely between cycles |
| Postmenopausal | 25.8 to 134.8 | consistently raised, the diagnostic clue |
| Adult men | 1.5 to 12.4 |
What it is
FSH is produced by the anterior pituitary in response to gonadotropin-releasing hormone from the hypothalamus. In women it stimulates ovarian follicles to grow each cycle and rises sharply as ovarian reserve falls during perimenopause. In men it acts on Sertoli cells to support spermatogenesis and is interpreted alongside testosterone and LH.
Why a clinician would order it
FSH is requested to investigate cycle irregularities or amenorrhoea, to confirm the menopause transition (particularly when symptoms are equivocal in women under 45), as part of fertility work-up in both sexes, and in suspected hypopituitarism. In men it adds context to a low testosterone reading by distinguishing primary testicular failure from pituitary causes.
If your level is outside the range
Symptoms of low FSH
- Amenorrhoea or oligomenorrhoea in young women (hypothalamic or pituitary cause)
- Reduced libido
- Reduced fertility (men: low sperm count)
What low can indicate. Hypothalamic amenorrhoea (low body weight, intense exercise, stress), hypopituitarism, hyperprolactinaemia, contraceptive use (oral contraceptive suppresses FSH).
Symptoms of high FSH
- Hot flushes, night sweats, irregular periods (perimenopause)
- Vaginal dryness, sleep disturbance, mood changes
- In men: small testes, infertility (primary testicular failure)
What high can indicate. Perimenopause or postmenopause (the commonest cause in women over 40), premature ovarian insufficiency (under 40), primary testicular failure in men. A single raised FSH in a perimenopausal woman is not diagnostic on its own; the picture is built from FSH, LH, oestradiol, symptoms, and cycle history.
Testing tips
Cycling women: drawn on days 2 to 5 of the cycle for a clean baseline (day 1 is the first day of bleeding). If cycles have stopped or become irregular, drawn at any time but interpreted with cycle history. Oral contraceptive suppresses the result, so hold for at least 6 weeks if a true baseline is needed. Always interpret alongside LH and oestradiol.
Where you can get this tested
Follicle Stimulating Hormone is included in the following WMG Health panels. Same-day appointments at our Harley Street clinic, with results clinician-reviewed.
Want a specific combination of markers we do not have a panel for? Build a custom panel and our clinicians will design one for you.
Sources
UK guidance our clinicians use when interpreting this marker.
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.