Lab result explainedHormonesLast updated November 8, 2026

FSH blood test: what high and low follicle-stimulating hormone levels mean

Follicle-stimulating hormone (FSH) (FSH) · Reproductive hormone panel (FSH, LH, estradiol, often prolactin, TSH and AMH) · reported in mIU/mL (milli-international units per millilitre; identical to IU/L)

Follicle-stimulating hormone (FSH) is made by the pituitary gland at the base of the brain. In women it tells the ovaries to grow a follicle and ripen an egg each month and to make estrogen; in men it tells the testes to make sperm. The level is read against the menstrual cycle: on day 2 to 4 of a period a normal FSH is roughly 3 to 10 mIU/mL, it peaks briefly at ovulation, and after menopause it settles at 25 to over 100 mIU/mL because the ovaries no longer respond. In men a normal FSH is about 1.5 to 12 mIU/mL throughout adult life.

FSH works by feedback. When the ovaries or testes make enough estrogen, inhibin and (in men) testosterone, the pituitary eases off. When they fail, whether from menopause, premature ovarian insufficiency, chemotherapy or testicular damage, the pituitary pushes harder and FSH climbs. That is why a high FSH is the classic signature of a gland that is not responding, and a low FSH, when the ovaries or testes are also under-performing, points instead to a problem in the pituitary or hypothalamus, or to something suppressing them such as low body weight, stress, high prolactin or hormone medication.

People most often look up FSH for one of three reasons: a day-3 FSH as part of a fertility work-up, where under 10 mIU/mL is reassuring and over 15 to 20 suggests a reduced ovarian reserve; an FSH to confirm menopause or perimenopause, where a single value is less useful than most people expect because it swings widely in the transition; and FSH with LH and testosterone in men being assessed for low testosterone or low sperm count. In each case FSH is interpreted alongside LH, estradiol or testosterone, and in women the timing in the cycle.

FSH at a glance

  • What it is: a pituitary hormone that stimulates follicle growth and estrogen production in the ovaries and sperm production in the testes.
  • Normal (women, day 2–4 of the cycle): about 3–10 mIU/mL; mid-cycle peak 5–20; luteal phase 1.5–8. Labs differ.
  • Menopause: usually above 25–30 mIU/mL on two tests, and often 50–130; perimenopause values swing between normal and high from month to month.
  • Men: about 1.5–12 mIU/mL; high FSH with low testosterone means testicular failure; high FSH alone usually means impaired sperm production.
  • Day-3 FSH for fertility: under 10 reassuring, 10–15 reduced ovarian reserve, over 15–20 poor response to IVF stimulation expected; AMH is now the preferred test.
  • Low FSH with low estradiol or testosterone points to the pituitary or hypothalamus: low body weight, over-exercise, stress, high prolactin, pituitary disease, or hormonal medication.

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What FSH measures

FSH is a glycoprotein hormone released in pulses by the anterior pituitary under the control of gonadotropin-releasing hormone (GnRH) from the hypothalamus. In the ovary it binds receptors on granulosa cells, recruiting a group of small follicles each cycle and driving one to dominance while they convert androgens to estradiol. In the testis it acts on Sertoli cells to support sperm maturation. Estradiol and inhibin B (from the ovary) and inhibin B (from the testis) feed back to suppress FSH; when follicle numbers fall, inhibin B falls first, which is why FSH rises in the early follicular phase years before periods stop.

The test is an automated immunoassay on a single blood sample, reported in milli-international units per millilitre (mIU/mL), which is the same as IU/L. Because FSH is pulsatile and cycle-dependent, timing is everything in women who menstruate: a value of 12 mIU/mL is normal at mid-cycle and raised on day 3. For fertility assessment it is drawn on day 2 to 4 of the cycle together with estradiol, because a high estradiol (over about 60 to 80 pg/mL) can suppress FSH into the normal range and hide a reduced ovarian reserve. In men, in post-menopausal women and in women without periods, timing does not matter.

Several things shift the result without any change in the gonads. Combined hormonal contraception, HRT and GnRH analogues suppress FSH; a test for menopause is unreliable while on the pill and should be done after at least 2 to 4 weeks off, or interpreted by symptoms instead. Biotin supplements can interfere with some assays. Hemolysed or old samples are not a problem for FSH, but a single value in perimenopause is: the Stages of Reproductive Aging Workshop (STRAW+10) criteria define the late menopausal transition by FSH above 25 mIU/mL on a random draw, and still recommend diagnosis by menstrual pattern rather than a one-off test.

Normal range for FSH

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

GroupTypical range (mIU/mL (milli-international units per millilitre; identical to IU/L))Notes
Women, early follicular phase (day 2–4)About 3–10 mIU/mL (lab ranges run from roughly 2.5–12.5)The 'day-3 FSH' used in fertility work-ups. Read with estradiol; a high estradiol can mask a high FSH.
Women, mid-cycle (ovulatory) peakAbout 5–20 mIU/mLA brief surge alongside LH around day 12–14; lasts about 1 to 2 days.
Women, luteal phaseAbout 1.5–8 mIU/mLSuppressed by progesterone and estradiol after ovulation.
Women, pregnancy and on combined hormonal contraceptionLow, often under 1–2 mIU/mLNot interpretable for menopause or ovarian reserve while on the pill, patch or ring.
Women, perimenopause (menopausal transition)Fluctuates; random values above 25 mIU/mL mark the late transitionMay be 8 one month and 40 the next; diagnosis is by cycle pattern, not a single FSH.
Women, post-menopauseAbout 25–135 mIU/mL (commonly 40–100)Levels peak 2 to 3 years after the last period and slowly drift down over decades.
Premature ovarian insufficiency (under 40)Above 25–40 mIU/mL on two tests at least 4 weeks apartWith absent or irregular periods for 4 or more months; ESHRE uses 25, older criteria 40.
Men, adultAbout 1.5–12 mIU/mLAbove 12–15 with normal testosterone suggests impaired sperm production; above 15–20 with low testosterone indicates primary testicular failure.
Children (prepubertal)Under about 3–4 mIU/mLRises at puberty; a raised FSH in a girl under 8 or boy under 9 with pubertal signs suggests central precocious puberty.

High FSH

A high FSH means the pituitary is working harder than usual to stimulate the ovaries or testes, which almost always means the gonads are responding less. In a woman in her late 40s or 50s with irregular or absent periods, hot flashes and night sweats, an FSH above 25 to 30 mIU/mL fits the menopausal transition and above 40 is typical of established menopause. In a woman under 40, the same values with absent or irregular periods for 4 months or more on two tests 4 weeks apart define premature ovarian insufficiency (POI), which affects about 1 percent of women and matters for fertility, bone and heart health, and the question of hormone replacement until the usual age of menopause.

In women still having regular periods, a day-3 FSH of 10 to 15 mIU/mL suggests the ovarian reserve is diminishing and a value above 15 to 20 predicts a poor response to IVF stimulation. FSH is a late and noisy marker of reserve, because it rises only when inhibin B has already fallen and because it varies from cycle to cycle; anti-Mullerian hormone (AMH) and an antral follicle count on ultrasound are now preferred. A high day-3 FSH does not mean you cannot conceive naturally, particularly if cycles are regular; it lowers the odds and shortens the window.

In men, FSH reflects the sperm-producing tubules. A high FSH with a normal testosterone usually means the Sertoli cells and germ cells are damaged (previous mumps orchitis, undescended testes, chemotherapy, varicocele, Y-chromosome microdeletions) and sperm count is likely to be low. A high FSH with a high LH and low testosterone means the whole testis is failing (primary hypogonadism), the commonest cause of which is Klinefelter syndrome (XXY), present in about 1 in 600 men and frequently undiagnosed until a fertility or testosterone work-up.

Common causes

  1. Menopause and the menopausal transition

    The number of ovarian follicles falls below the threshold needed to make inhibin B and estradiol, and FSH rises from the late 30s onward, with random values above 25 mIU/mL in the late transition and 40–130 after the final period. Average age at menopause in the US is 51.

  2. Premature ovarian insufficiency

    Loss of ovarian function before 40, affecting about 1 in 100 women (1 in 1,000 before 30). Causes include Turner syndrome and other X-chromosome abnormalities, fragile X premutation (FMR1), autoimmune oophoritis (often with thyroid or adrenal autoimmunity), chemotherapy, pelvic radiation and ovarian surgery; about 70 to 90 percent are unexplained.

  3. Diminished ovarian reserve

    A smaller than expected pool of follicles for age, with regular cycles still occurring. Day-3 FSH of 10–20 mIU/mL, often with a low AMH (under 1 ng/mL) and a short cycle length (under 25 days) as the follicular phase shortens.

  4. Chemotherapy, radiation and ovarian or testicular surgery

    Alkylating agents (cyclophosphamide, busulfan), pelvic or total-body radiation and removal of ovarian tissue destroy follicles; in men the same treatments damage spermatogenesis, raising FSH first and testosterone-dependent LH later.

  5. Turner syndrome, Klinefelter syndrome and other chromosomal disorders

    In Turner syndrome (45,X) the ovaries regress before puberty and FSH is high from childhood; in Klinefelter syndrome (47,XXY) FSH and LH are high with small firm testes, low or low-normal testosterone and near-absent sperm.

  6. Primary testicular failure in men

    Mumps orchitis after puberty, testicular torsion or trauma, undescended testes, anabolic steroid-related damage, varicocele and genetic causes such as Y-chromosome microdeletions raise FSH; the higher the FSH, the lower the chance of finding sperm.

  7. Autoimmune and infiltrative disease

    Autoimmune oophoritis, often with Addison's disease, Hashimoto's thyroiditis or type 1 diabetes, causes POI; galactosemia and some metabolic disorders damage the ovary; hemochromatosis more often causes low FSH through pituitary iron deposition but can affect the gonads too.

  8. FSH-secreting pituitary adenoma (rare)

    Some non-functioning pituitary tumours secrete FSH or its subunits; in women this can cause ovarian hyperstimulation and large cysts with a high FSH, high estradiol and low LH, an unusual combination that points to the diagnosis.

  9. Mid-cycle timing or sampling error

    FSH doubles or triples for a day or two at ovulation; a value of 15 mIU/mL drawn on day 13 is normal. Confirm which day of the cycle the sample was taken before interpreting a 'high' result.

Symptoms that can go with it

  • Irregular, skipped or absent periods, or cycles becoming shorter (under 25 days) in the early transition
  • Hot flashes, night sweats and sleep disturbance
  • Vaginal dryness, pain with sex, urinary urgency and reduced libido
  • Difficulty conceiving or a poor response to fertility treatment
  • Mood changes, irritability, brain fog and joint aches during the menopausal transition
  • In men: low sperm count or infertility, small or soft testes, and with low testosterone, low libido, erectile difficulty, fatigue and loss of muscle
  • In girls or boys: early breast development or testicular enlargement before 8 or 9 (precocious puberty), or absent puberty by 13 to 14 with a high FSH (gonadal failure)

Low FSH

A low FSH is normal in several situations: during pregnancy, on the combined pill or other hormonal contraception, in the luteal phase of the cycle, in children before puberty, and in men on testosterone or anabolic steroids, which switch the pituitary off. In these settings it needs no further thought. A low FSH matters when it is accompanied by low estradiol in a woman with absent periods, or low testosterone in a man, because then the pituitary is failing to respond to a gonad that is asking for stimulation. That pattern is called hypogonadotropic (secondary or central) hypogonadism.

The commonest cause in women is functional hypothalamic amenorrhea: low body weight or rapid weight loss, an eating disorder, intense exercise, or sustained psychological stress reduce GnRH pulses, and FSH, LH and estradiol all fall; periods stop and bone density is lost. High prolactin from a pituitary microadenoma or from antipsychotic and anti-nausea drugs does the same. In polycystic ovary syndrome FSH is typically low-normal with a relatively high LH (a ratio above 2:1 was once used diagnostically, though it is no longer required), and estradiol is normal rather than low. Pituitary tumours, surgery, radiation, head injury, Sheehan's syndrome after a difficult delivery, iron overload from hemochromatosis, and congenital conditions such as Kallmann syndrome (absent puberty with no sense of smell) are the structural causes.

In men, a low or inappropriately normal FSH and LH with a low testosterone is the pattern seen with obesity, obstructive sleep apnea, opioids, glucocorticoids, anabolic steroid use (including months after stopping), high prolactin and pituitary disease. Because FSH and LH do not rise, the problem is above the testes, and treating the cause (weight loss, stopping the drug, treating prolactin) often restores testosterone without hormone replacement.

Common causes

  1. Hormonal contraception, HRT and GnRH analogues

    The combined pill, patch, ring and most HRT regimens suppress FSH to very low levels; GnRH agonists (leuprolide) and antagonists used for endometriosis, fibroids and prostate cancer switch it off completely. Allow 2 to 4 weeks off before testing for menopause.

  2. Pregnancy

    Placental hCG and high estrogen and progesterone suppress FSH throughout pregnancy; a low FSH with a missed period should prompt a pregnancy test before anything else.

  3. Functional hypothalamic amenorrhea

    Low energy availability from under-eating, weight loss (often to a BMI under 18.5 or a loss of 10 percent of body weight), high training loads or stress reduce GnRH pulses. FSH and LH are low or low-normal, estradiol is low and periods stop; it is the commonest cause of secondary amenorrhea in young women after pregnancy and PCOS.

  4. Hyperprolactinemia

    Prolactin above about 25 ng/mL suppresses GnRH. Causes include prolactin-secreting pituitary adenomas, antipsychotics (risperidone, haloperidol), metoclopramide, some antidepressants, hypothyroidism and chronic kidney disease. Milky nipple discharge is a clue but is absent in many.

  5. Polycystic ovary syndrome

    FSH is low-normal while LH is relatively high and androgens are raised; the FSH itself is not low enough to be diagnostic, but the pattern of normal estradiol, high LH:FSH ratio and irregular cycles distinguishes PCOS from hypothalamic amenorrhea.

  6. Pituitary tumours, surgery, radiation and infiltration

    Non-functioning adenomas, craniopharyngiomas, pituitary surgery, cranial radiotherapy, sarcoidosis, hemochromatosis, lymphocytic hypophysitis and immune checkpoint inhibitor drugs damage gonadotroph cells; FSH and LH are usually the first pituitary hormones to fail, followed by growth hormone, TSH and ACTH.

  7. Testosterone, anabolic steroids, opioids and glucocorticoids in men

    Exogenous testosterone and anabolic steroids suppress FSH and LH to near zero and shut down sperm production, often for 6 to 18 months after stopping; long-term opioids and high-dose steroids suppress GnRH and lower testosterone with low FSH and LH.

  8. Kallmann syndrome and congenital hypogonadotropic hypogonadism

    Failure of GnRH neurons to develop causes absent puberty with low FSH, LH and sex steroids; in Kallmann syndrome the sense of smell is absent or reduced. Diagnosed in adolescence when puberty has not started by 13 to 14.

  9. Severe illness, obesity and sleep apnea

    Critical illness, uncontrolled diabetes, cirrhosis and marked obesity blunt GnRH pulses; in men with a BMI over 35, testosterone is commonly low with low-normal FSH and LH, and weight loss of 10 percent or more raises testosterone by several nmol/L.

Symptoms that can go with it

  • Absent or very infrequent periods in a woman who is not pregnant or on hormonal contraception
  • Low estrogen symptoms: vaginal dryness, hot flashes, low libido and, over time, bone loss and stress fractures
  • Difficulty conceiving, with no ovulation on tracking
  • Milky nipple discharge, headaches or visual field loss (prolactinoma or other pituitary tumour)
  • Weight loss, restrictive eating, intense exercise or high stress preceding the loss of periods
  • In men: low libido, erectile dysfunction, fatigue, loss of morning erections, reduced muscle and body hair, small soft testes and infertility
  • In adolescents: no breast development by 13 or no testicular growth by 14, with or without a poor sense of smell

Read it alongside

  • LH (luteinizing hormone) — released from the same cells; both high means gonadal failure, both low means a pituitary or hypothalamic cause, and a high LH:FSH ratio with normal estradiol suggests PCOS.
  • Estradiol — the ovarian response; a day-3 estradiol above 60–80 pg/mL can suppress FSH and hide a reduced reserve, and low estradiol with low FSH confirms a central cause.
  • AMH (anti-Mullerian hormone) — a steadier, cycle-independent marker of ovarian reserve that has largely replaced day-3 FSH for predicting IVF response.
  • Testosterone — in men, the combination of FSH, LH and total (and free) testosterone separates primary testicular failure from a pituitary or lifestyle cause.
  • Prolactin — a high prolactin suppresses FSH and LH and is a common, treatable cause of absent periods and low testosterone.
  • TSH — thyroid disease disrupts cycles and can raise prolactin; always checked alongside FSH for irregular or absent periods.
  • hCG (pregnancy test) — mandatory before interpreting a low FSH or absent periods in any woman who could be pregnant.
  • Karyotype and FMR1 testing — ordered when FSH is high before 40 (Turner syndrome, fragile X premutation) or in men with very high FSH and small testes (Klinefelter syndrome).

What usually happens next

  1. If you still have periods, confirm which day of the cycle the sample was drawn; for ovarian reserve or menopause questions a repeat on day 2 to 4 with estradiol (and ideally AMH) is standard.
  2. A single raised FSH in your 40s with irregular periods is usually enough to confirm the menopausal transition when symptoms fit; no further tests are needed and treatment is decided by symptoms, not the number.
  3. A raised FSH before 40 is repeated after at least 4 weeks; if still above 25 mIU/mL with absent or irregular periods, expect a karyotype, fragile X (FMR1) premutation test, thyroid and adrenal antibodies, and a discussion about hormone replacement and fertility options including egg donation.
  4. A low FSH with low estradiol or testosterone prompts prolactin, TSH, a review of weight, exercise, stress, medications and drugs (including anabolic steroids), and if no cause is found, the rest of the pituitary hormones and an MRI of the pituitary.
  5. For fertility, a high day-3 FSH or low AMH is a reason to seek a fertility specialist sooner rather than later, particularly over 35, since the window may be shorter than average.
  6. In men with a low sperm count, FSH guides the next steps: a very high FSH with small testes points to a genetic cause and karyotype or Y-microdeletion testing; a normal FSH with no sperm suggests a blockage that may be surgically treatable.

Diet, lifestyle and natural levers with evidence

What can move FSH once the cause is known. Nothing here replaces finding the cause.

Restore energy balance in hypothalamic amenorrhea (weight, food, training load)

Strong evidence

When low FSH, LH and estradiol come from under-eating or over-training, increasing energy intake and reducing training restores GnRH pulses: in cohort and intervention studies, 60 to 80 percent of women regained periods within 6 to 12 months of gaining weight (typically back above a BMI of 19 to 20 or regaining the lost 5 to 10 percent) and cutting exercise volume, with recovery of bone density following. Cognitive behavioural therapy aimed at stress and eating attitudes restored ovulation in 6 of 8 women versus 1 of 8 controls in a small randomised trial. This is the only lever that fixes the problem rather than masking it.

The combined pill restores bleeding but does not treat the cause or reliably restore bone density; discuss with your clinician before using it to 'regulate' periods.

Weight loss when overweight with PCOS or low testosterone

Strong evidence

In women with PCOS, losing 5 to 10 percent of body weight restores ovulation in roughly half within 6 months in lifestyle trials, normalising the LH:FSH pattern and lowering androgens. In men with obesity-related low testosterone and low-normal FSH and LH, weight loss of 10 percent raises total testosterone by about 2 to 3 nmol/L (60 to 90 ng/dL) in meta-analyses, and bariatric surgery raises it by 8 to 10 nmol/L. FSH itself moves little; the ovaries and testes respond better to it.

Stop smoking

Strong evidence

Smoking is toxic to ovarian follicles. Smokers have higher early-follicular FSH than non-smokers at every age in population studies, reach menopause 1 to 2 years earlier on average, and have about 1.5 times the odds of premature ovarian insufficiency; smoking also lowers IVF success by roughly a third per cycle. In men, smoking reduces sperm count and motility by 10 to 20 percent in meta-analyses. Quitting does not restore lost follicles but removes an ongoing accelerant.

Soy isoflavones (for FSH and menopausal symptoms)

Moderate evidence

A meta-analysis of 47 randomised trials found that soy isoflavones lowered FSH by about 20 percent and LH by about 20 percent in premenopausal women, with no significant change in estradiol and no effect on FSH in postmenopausal women. In postmenopausal women, 30 to 80 mg a day of isoflavones for 12 weeks or more reduces hot flash frequency by about 20 percent beyond placebo in pooled analyses. The FSH reduction has not been shown to change fertility or delay menopause.

Soy foods are safe for most people including breast cancer survivors in current evidence; concentrated isoflavone supplements should be discussed with your oncologist if you have had estrogen-sensitive cancer. Soy reduces levothyroxine absorption if taken at the same time.

DHEA for diminished ovarian reserve

Preliminary evidence

Dehydroepiandrosterone 75 mg a day for 6 to 16 weeks before IVF has been studied in women with high FSH or low AMH; pooled analyses of small randomised trials suggest higher clinical pregnancy rates (roughly 1.5 to 2 times) and lower cycle cancellation, but the trials are small, several are of low quality, and a 2015 Cochrane review found the evidence insufficient to recommend it. FSH itself typically falls only slightly. It does not reverse premature ovarian insufficiency.

DHEA is a hormone: acne, oily skin, hair growth and mood changes are common, and it should not be taken with a history of hormone-sensitive cancer or without fertility specialist supervision.

Coenzyme Q10 for ovarian and sperm quality

Preliminary evidence

In a randomised trial of 186 women with poor ovarian reserve, 600 mg a day of CoQ10 for 60 days before IVF produced more retrieved eggs, better-quality embryos and lower cancellation rates than no pretreatment, with a small fall in day-3 FSH; a meta-analysis of 5 trials found higher clinical pregnancy rates. In men, 200 to 300 mg a day for 3 to 6 months improves sperm concentration and motility in randomised trials, though effects on live birth are unproven.

Can reduce the effect of warfarin; otherwise well tolerated.

When to see a clinician promptly

  • Absent periods for 3 months or more (or 6 months if cycles were irregular) in anyone not pregnant or on hormonal contraception, and any raised FSH before the age of 40.
  • Sudden severe headache, double vision or loss of peripheral vision with a low FSH: possible pituitary tumour or pituitary apoplexy, which needs urgent assessment.
  • A raised FSH with heavy, prolonged or unpredictable bleeding in the menopausal transition, or any vaginal bleeding more than 12 months after your last period, which must be investigated for endometrial cancer.
  • Loss of periods with weight loss, restrictive eating or compulsive exercise, particularly with fainting, a slow pulse or stress fractures.
  • In men, a high FSH with a lump or swelling in a testicle, or a low FSH with low testosterone and visual, headache or breast symptoms.
  • No signs of puberty by 13 in a girl or 14 in a boy, or signs of puberty before 8 or 9, with any FSH result.

Frequently asked questions

What is a normal FSH level by age?

In women, the day-3 FSH is similar from the teens to the mid-30s at about 3 to 8 mIU/mL, drifts up to 6 to 10 in the late 30s and early 40s as follicle numbers fall, swings between normal and over 25 during the menopausal transition (typically ages 45 to 55), and settles at 40 to 130 after menopause. In men it stays at about 1.5 to 12 mIU/mL from puberty onward, rising slightly after 60. Children before puberty are under about 3 to 4.

What FSH level indicates menopause?

An FSH above 25 to 30 mIU/mL on a random sample is used by the STRAW+10 staging system to mark the late menopausal transition, and most women past their final period have levels of 40 to 130. However, FSH fluctuates so much in perimenopause that a normal value does not rule out the transition and a single high value does not confirm menopause. In women over 45, guidelines (including NICE and ACOG) recommend diagnosing menopause from 12 months without periods and symptoms, without an FSH; the test is reserved for women under 45, those with a hysterectomy or on hormonal contraception where cycle history is not available.

What is a good day-3 FSH for fertility or IVF?

A day-3 FSH under 10 mIU/mL with an estradiol under 60 to 80 pg/mL is considered reassuring. Values of 10 to 15 suggest diminished ovarian reserve and a reduced but real chance of success; values above 15 to 20 predict a poor response to IVF stimulation and many clinics will discuss alternatives, including donor eggs, above 20 to 25. FSH varies from cycle to cycle and the highest value you have ever had is the most informative. AMH and an antral follicle count give a more stable picture and are now preferred.

Can I get pregnant with high FSH?

Yes, though the odds are lower. A high day-3 FSH tells you the pool of remaining eggs is smaller and the response to fertility drugs will be weaker; it says less about egg quality, which depends mainly on age. Women under 35 with a high FSH do better than women over 40 with a normal FSH. Even in premature ovarian insufficiency, about 5 to 10 percent of women conceive spontaneously, which is why contraception is still discussed if pregnancy is not wanted. Donor eggs give high success rates regardless of FSH.

What does low FSH mean in a woman?

If you are pregnant, on the pill, or in the luteal half of your cycle, it is expected. If you have no periods and a low estradiol, it means the pituitary is not driving the ovaries, most often because of low body weight, over-exercise or stress (hypothalamic amenorrhea), high prolactin, or less commonly pituitary disease. A low-normal FSH with a high LH and irregular cycles fits PCOS. The next tests are a pregnancy test, prolactin, TSH, LH and estradiol.

What does high FSH mean in a man?

FSH in men mainly reflects sperm production. A high FSH (above about 12 to 15 mIU/mL) with normal testosterone and LH means the sperm-producing tubules are damaged and the sperm count is likely to be low or zero; the higher the FSH, the less likely sperm can be retrieved. A high FSH with high LH and low testosterone means the whole testis is failing (primary hypogonadism), and Klinefelter syndrome is the commonest cause, so a karyotype is usually done. A high FSH alone does not cause symptoms.

Can FSH levels be lowered?

FSH is a response, not a cause, so lowering it artificially (with estrogen, the pill or GnRH analogues) does not restore ovarian function or egg numbers; it just removes the signal. Soy isoflavones lower FSH by about 20 percent in premenopausal women without improving fertility, and DHEA or CoQ10 before IVF may improve the ovaries' response with only small changes in FSH. The exceptions are a high FSH caused by smoking, which stops rising when you quit, and a low FSH caused by under-eating or over-training, which recovers with energy balance.

Do I need to test FSH on a specific day?

Yes if you have cycles and the question is ovarian reserve or menopause: day 2 to 4 (counting the first day of full bleeding as day 1), together with estradiol. A value drawn mid-cycle will be falsely high and one drawn in the luteal phase falsely low. If you have no periods, are post-menopausal or are a man, any day is fine. Stop combined hormonal contraception for at least 2 to 4 weeks first if the test is for menopause, and mention biotin supplements, which can interfere with some assays.

References

  1. Follicle-stimulating hormone (FSH) levels test. MedlinePlus, US National Library of Medicine (2023)View source
  2. Harlow SD, Gass M, Hall JE, et al.. Executive summary of the Stages of Reproductive Aging Workshop + 10: addressing the unfinished agenda of staging reproductive aging. Journal of Clinical Endocrinology and Metabolism (2012)
  3. European Society for Human Reproduction and Embryology Guideline Group on POI. ESHRE guideline: management of women with premature ovarian insufficiency. Human Reproduction (2016)
  4. Practice Committee of the American Society for Reproductive Medicine. Testing and interpreting measures of ovarian reserve: a committee opinion. Fertility and Sterility (2020)
  5. Gordon CM, Ackerman KE, Berga SL, et al.. Functional hypothalamic amenorrhea: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism (2017)
  6. Bhasin S, Brito JP, Cunningham GR, et al.. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism (2018)
  7. Menopause: diagnosis and management (NG23). National Institute for Health and Care Excellence (2024)
  8. Hooper L, Ryder JJ, Kurzer MS, et al.. Effects of soy protein and isoflavones on circulating hormone concentrations in pre- and post-menopausal women: a systematic review and meta-analysis. Human Reproduction Update (2009)
  9. Sun L, Tan L, Yang F, et al.. Active smoking and the risk of early menopause: a meta-analysis. Menopause (2012)
  10. Xu Y, Nisenblat V, Lu C, et al.. Coenzyme Q10 restores oocyte mitochondrial function and fertility during reproductive aging; and pretreatment with CoQ10 improves ovarian response in women with poor ovarian reserve: a randomized controlled trial. Reproductive Biology and Endocrinology (2018)
  11. Nagels HE, Rishworth JR, Siristatidis CS, Kroon B. Androgens (dehydroepiandrosterone or testosterone) for women undergoing assisted reproduction. Cochrane Database of Systematic Reviews (2015)
  12. Male hypogonadism. Merck Manual Professional Version (2024)

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.