Why does the menstrual cycle day matter for FSH?

FSH varies markedly across the cycle, so in women a result is interpretable only with the cycle day recorded. Ovarian reserve assessment specifically uses early-follicular sampling on day 2–5.

How is FSH used to assess menopause?

A persistently elevated FSH, together with menstrual change and symptoms, supports a menopausal or perimenopausal picture, reflecting reduced ovarian feedback. It is interpreted alongside oestradiol and the clinical presentation.

How does FSH distinguish primary from secondary hypogonadism?

In primary gonadal failure, reduced feedback drives FSH up alongside low gonadal hormones, while in secondary central causes FSH is low or inappropriately normal despite low gonadal hormones. LH is measured with it to clarify the pattern.

Is fasting required for the FSH test?

No. Fasting is not required. In women the cycle day should be recorded, and use of hormonal contraceptives, hormone therapy, GnRH analogues, and high-dose biotin should be documented.

Can medications affect FSH results?

Yes. Oestrogen-containing contraceptives and hormone therapy suppress FSH through feedback, GnRH analogues alter gonadotrophin release, and high-dose biotin can interfere with some immunoassays.

How long does it take to get FSH results?

Results are typically available within 1–3 business days from specimen receipt at the processing laboratory.

Why is FSH usually measured with LH?

The two gonadotrophins are almost always assessed together because their relative pattern helps localise dysfunction — both are elevated in primary gonadal failure and both are low or inappropriately normal in central causes.

BML-HRF-008female hormonesUSA

Follicle-Stimulating Hormone (FSH) Test

The Follicle-Stimulating Hormone (FSH) test measures a pituitary gonadotrophin that regulates ovarian follicular development in women and spermatogenesis in men. It helps distinguish primary gonadal failure, where FSH rises from reduced feedback, from secondary central causes, where FSH is low or inappropriately normal.

Biomarkers

Blood (serum)

Sample

1–3 business days

Turnaround

Fasting

What is the FSH test?

The FSH Test measures follicle-stimulating hormone, a pituitary gonadotrophin that regulates ovarian follicular development in women and supports spermatogenesis in men. As a marker of the hypothalamic-pituitary-gonadal axis, it helps localise the level at which reproductive or gonadal dysfunction arises. In the diagnostic landscape, FSH is a first-line investigation in the workup of menstrual disturbance, suspected menopause or primary ovarian insufficiency, infertility, and hypogonadism in both sexes. Its principal interpretive value lies in distinguishing primary gonadal failure — where reduced negative feedback drives FSH up — from secondary, central causes, where FSH is low or inappropriately normal alongside low gonadal hormones. It is almost always measured together with LH and the relevant sex steroids, and in women the result is meaningful only in relation to the menstrual cycle phase or menopausal status.

What does the FSH test measure?

FSH(Follicle-Stimulating Hormone)

Range: Highly cycle-phase, sex- and age-specific. Premenopausal follicular phase ~3.5–12.5 mIU/mL; postmenopausal ~25.8–134.8 mIU/mL; adult men ~1.5–12.4 mIU/mL # REVIEWER FLAG: FSH intervals are strongly phase-, sex- and age-banded and assay-specific — reviewer to confirm against Access Medical Laboratories assay-specific ranges before publication.Optimal: Interpreted against cycle phase, sex, and age rather than a single optimum # REVIEWER FLAG: No standardised functional optimal — reviewer to confirm.mIU/mL / IU/L

Follicle-stimulating hormone is a glycoprotein gonadotrophin secreted by the anterior pituitary under pulsatile gonadotrophin-releasing hormone (GnRH) control, with feedback from gonadal steroids and inhibin. In women it drives ovarian follicular recruitment and growth and varies sharply across the menstrual cycle; in men it stimulates Sertoli cells and supports spermatogenesis. It is secreted in pulses and shares a common alpha subunit with LH, TSH, and hCG, with biological specificity conferred by its beta subunit.

FSH is central to evaluating the hypothalamic-pituitary-gonadal axis. A raised FSH indicates reduced gonadal feedback, as in primary ovarian insufficiency, menopause, or primary testicular failure, whereas a low or inappropriately normal FSH in the face of low gonadal hormones points to a hypothalamic or pituitary (secondary) cause. It is interpreted with LH and the relevant gonadal steroids, and timing within the menstrual cycle is essential in women.

Why is the FSH test ordered?

Evaluation of suspected menopause or perimenopause in women with menstrual change and vasomotor symptoms
Investigation of suspected primary ovarian insufficiency in women under 40 with oligomenorrhoea or amenorrhoea
Female infertility workup, including assessment of ovarian reserve when interpreted with early-follicular sampling and supporting markers
Assessment of amenorrhoea or oligomenorrhoea to distinguish ovarian, pituitary, and hypothalamic causes
Male infertility evaluation and assessment of spermatogenic function alongside LH and testosterone
Investigation of hypogonadism in men to distinguish primary testicular failure from secondary pituitary or hypothalamic causes
Evaluation of delayed or precocious puberty as part of a gonadotrophin assessment
Investigation of suspected pituitary dysfunction where gonadotrophin output is being characterised

Sample collection and turnaround

Sample type

Blood (serum)

Fasting required

Collection method

Venipuncture at patient service centre

Turnaround

1–3 business days

Collection notes

In women, record the menstrual cycle day; ovarian reserve assessment uses early-follicular (day 2–5) sampling, and the cycle phase must accompany the request. Document use of hormonal contraceptives, hormone therapy, GnRH analogues, and high-dose biotin. FSH is usually measured together with LH and the relevant sex steroids.

Specimen requirements

Minimum 0.5 mL serum. Separate serum from cells within 2 hours of collection.

What can affect FSH results?

variableMenstrual cycle phase

FSH changes markedly across the cycle, with a mid-cycle surge and distinct follicular and luteal levels, so in women results are interpretable only with the cycle day. Ovarian reserve assessment uses early-follicular (day 2–5) sampling.

reducesOestrogen-containing contraceptives and hormone therapy

Exogenous oestrogen and progestogen suppress gonadotrophin secretion through negative feedback, lowering FSH and obscuring the underlying axis. A washout interval may be required for meaningful assessment.

variableGnRH agonists and antagonists

These agents alter pituitary gonadotrophin release — initial stimulation then suppression with agonists, and direct suppression with antagonists — substantially changing FSH depending on agent and timing.

variableBiotin supplementation

High-dose biotin can interfere with streptavidin-biotin immunoassay platforms, producing falsely elevated or reduced FSH depending on assay design.

variablePulsatile secretion

Because FSH is released in pulses, a single measurement may not capture the average level; borderline results may warrant repeat or paired LH sampling.

variableHeterophile antibodies

Endogenous antibodies can interfere with immunoassay measurement, producing spurious results that are discordant with the clinical picture. # REVIEWER FLAG: Confirm assay susceptibility and mitigation with Access Medical Laboratories.

What do FSH results mean?

Elevated

An elevated FSH indicates reduced gonadal negative feedback — in women, menopause or primary ovarian insufficiency; in men, primary testicular failure. In the reproductive workup, a high early-follicular FSH suggests diminished ovarian reserve. Marked elevation with low gonadal steroids confirms a primary gonadal cause.

Normal

A normal FSH, interpreted with cycle phase, LH, and gonadal steroids, is consistent with an intact axis. In women, normal values must be read against the menstrual day, and a normal result does not exclude subtle ovarian reserve decline when other markers are abnormal.

Reduced

A low or inappropriately normal FSH in the presence of low gonadal hormones points to a secondary (hypothalamic or pituitary) cause, such as hypogonadotrophic hypogonadism or pituitary insufficiency. Suppression from exogenous sex steroids should be excluded.

Note: FSH must be interpreted with the menstrual cycle phase in women and always alongside LH and the relevant gonadal steroids; it is rarely diagnostic in isolation. Pulsatile secretion means a single value can mislead, and exogenous hormones suppress the result. Reference ranges differ sharply by sex, age, and cycle phase, so the correct interval must be applied.

Frequently asked questions

It measures follicle-stimulating hormone, a pituitary gonadotrophin that drives ovarian follicular development in women and supports spermatogenesis in men. It is a key marker of the hypothalamic-pituitary-gonadal axis.

How to access the FSH test

The FSH reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.

Create Free Account

About this page

Published: June 3, 2026

Last reviewed: June 3, 2026

References:

This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.

Related tests

female hormones

AMH

The AMH test measures Anti-Müllerian hormone, a granulosa-cell glycoprotein whose level reflects the pool of small growing ovarian follicles and serves as an indirect index of ovarian reserve. Measured here from a capillary dried blood spot, it supports fertility counselling, prediction of ovarian response, and the assessment of PCOS.

BML-HRF-014View reference →

male hormones

Testosterone Panel (LC-MS/MS)

The Testosterone, Free, Bioavailable and Total (LC-MS/MS) Test measures all three circulating fractions using the gold-standard LC-MS/MS method. It is ordered to diagnose male hypogonadism, resolve equivocal total-testosterone results when SHBG is altered, assess hyperandrogenism in women, and monitor replacement therapy, with superior specificity and sensitivity to immunoassay.

BML-HRM-001View reference →