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Follicle-Stimulating Hormone (FSH)

A pituitary hormone that helps run the menstrual cycle in women and sperm production in men. It rises after menopause.

AI-verified against cited sources. Awaiting expert reviewAlso called FSHLOINC 15067-2

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What it is

Follicle-stimulating hormone (FSH) is made by the pituitary gland, a small gland at the base of the brain. In women, it helps eggs grow in the ovaries each cycle. In men, it helps the testes make sperm. The pituitary adjusts how much FSH it makes based on signals from the ovaries or testes. FSH often rises when they aren't responding well, and it falls when the pituitary or the brain area that signals it (the hypothalamus) makes less.

Why it matters

FSH is mostly checked together with LH and estradiol. It helps clinicians look into why periods are irregular or have stopped, how the ovaries are doing, whether menopause or perimenopause may be starting, and whether a low sperm count may come from the testes or from the brain's signals. In children, it helps look into puberty that starts very early or late. A single result is a snapshot, because FSH moves through the cycle and swings in perimenopause.

If it’s low

A low FSH can mean the pituitary, or the part of the brain that signals it, is making less. It's also seen with some hormone medicines, very low body weight and very heavy exercise, and many of these causes can be temporary. A clinician can look at it alongside LH, estradiol or testosterone.

Common causes

  • Hormonal birth control, or estrogen or testosterone treatment
  • Rapid weight loss, being very underweight, or very heavy exercise
  • Severe physical or emotional stress
  • A problem with the pituitary gland or the hypothalamus, including tumors
  • Inherited conditions such as Kallmann syndrome

What can help

  • Ask your clinician whether other pituitary and sex hormones should be checked
  • Ask whether your weight, exercise or stress could be playing a part
  • Bring a list of your medicines and hormones to the visit

If it’s high

A high FSH usually means the ovaries or testes aren't responding as strongly to the pituitary's signal, so the pituitary makes more FSH to try to compensate. After menopause, this is expected. Before menopause, a high result is worth talking about with a clinician, who will often repeat the test and look at your periods, symptoms and other hormones.

Common causes

  • Menopause and perimenopause (a normal rise with age)
  • The brief peak around mid-cycle in women who still have periods
  • Primary ovarian insufficiency (ovaries slowing down before age 40)
  • Damage to the ovaries or testes from chemotherapy, radiation, injury, an infection such as mumps, or an autoimmune condition
  • Chromosome conditions such as Turner syndrome or Klinefelter syndrome
  • Surgical removal of the ovaries or testes
  • In men, testicular failure or a testicular tumor

What can help

  • Ask your clinician whether the test should be repeated, and when
  • Ask whether LH, estradiol, AMH or testosterone should be checked too
  • Bring a list of your medicines and hormones, since they can change FSH

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex and age. Choose women or men to see the one that applies.

Children and teens 8 ranges

See FSH by age and sex, with the U.S. survey numbers where they exist.

If this applies to you

FSH means a little more for some people. Open the one that fits you.

Trying to conceive

ASRM suggests measuring FSH together with estradiol on days 2 to 4 of the cycle, and NICE offers FSH and LH when cycles are irregular. NICE says FSH should not be used to predict how the ovaries will respond to IVF or how IVF will turn out.

Blood tests for trying to conceive, including IVF

Perimenopause or menopause

If you are 45 or over with typical symptoms, NICE says perimenopause and menopause can be recognized without blood tests. It suggests an FSH test only for people aged 40 to 45 with symptoms and cycle changes, or under 40 when early menopause is possible.

Blood tests in perimenopause and menopause

On testosterone therapy

Testosterone therapy is linked to lower sperm production, the Endocrine Society says. The FDA label for one testosterone gel notes that LH and FSH fell during treatment, and that large doses can lower sperm production by turning down FSH.

Blood tests on testosterone therapy

How common is your level?

NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.

How FSH varies with age in the U.S.Shaded: middle 90% and middle 50% of people. Line: the median. mIU/mL. Point at any age, or focus the chart and use the arrow keys, to read both sexes in words.

Use the left and right arrow keys to read each age. Shift moves five years.

Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2017-March 2020 (pre-pandemic), August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.

Explore FSH by age and sex: every percentile as a table, with a download.

What can affect your result

  • Menstrual cycle day: FSH rises briefly around ovulation and is lowest in the second half of the cycle
  • Age and menopause status: levels climb as ovarian function declines
  • Hormonal birth control, estrogen or testosterone treatment and other hormone medicines
  • Body weight, heavy exercise and severe stress
  • Pulsatile release: levels change from hour to hour
  • Assay method: ranges differ between labs
  • High-dose biotin supplements can interfere with some assays. Labcorp advises stopping biotin at least 72 hours before the draw unless your clinician says otherwise, while Mayo reports its FSH assay is not affected up to 1200 ng/mL of biotin.
  • Hormonal birth control, estrogen or testosterone treatment and other hormone medicines can lower FSH, so the result may not show what your body does on its own.
  • FSH is released in pulses, so one sample may not match your average level.
  • People treated with mouse monoclonal antibodies, or who had them for imaging, can get erroneous results with some assays.

Any time of day. If you still have periods, ask which cycle day to test: early in the cycle is common for fertility questions, and the ESHRE guideline says timing isn't needed when checking for premature ovarian insufficiency. Reflects the current feedback between the brain and the ovaries or testes. In perimenopause it can swing from month to month, so one result is a snapshot.

When to talk to a clinician

Talk with a clinician if you've missed more than one period and you aren't pregnant, if you have menopause-like symptoms such as hot flashes or irregular periods before age 45 (especially before 40), or if you've been trying to conceive for 12 months without success. For children, talk with a clinician if puberty starts before age 8 (girls) or 9 (boys), or hasn't started by age 13 (girls) or 14 (boys).

Questions you could ask

  • On which day of my cycle should the blood be drawn?
  • How does this result fit with my periods and symptoms?
  • Could my age, cycle day or a medicine explain this result?
  • Should we repeat the test, and when?
  • Should we check LH, estradiol or other hormones too?
  • Could my weight, exercise, stress or a medicine explain this result?

Questions people ask

Does a high FSH mean I'm in menopause?

Not by itself. FSH rises after menopause, but in perimenopause it can swing from high to usual from one month to the next, and it also peaks briefly at mid-cycle. Some guidelines treat a level above 25 IU/L as one supporting sign, together with changes in your periods, and a repeat test 4 to 6 weeks later may be needed. Your clinician can put your number in context.

Why does my cycle day matter for an FSH test?

FSH changes across the menstrual cycle, with a short peak around ovulation. Labs print different ranges for the early, mid-cycle and later phases. For some fertility questions, clinicians ask for a blood draw early in the cycle. If you don't have regular periods, the timing is less important.

Is IU/L different from mIU/mL?

No. They are the same number, so 8.0 mIU/mL is the same as 8.0 IU/L and no conversion is needed. Some labs print the unit as U/L.

Does FSH matter for men?

Yes. In men, FSH helps the testes make sperm. A clinician may check FSH with LH and testosterone when a man has a low sperm count, trouble conceiving or low testosterone, to help tell whether the cause is in the testes or in the brain's signals.

Can birth control or hormone therapy change my FSH?

Yes. Hormonal birth control and some other hormone medicines can lower FSH and LH, so the result may not show what your body would do on its own. NICE advises against using FSH to identify menopause in people on combined hormonal contraception. Tell the person ordering the test about everything you take.

Show the science and sources

Units

  • 1 mIU/mL = 1 mIU/mL
  • 1 mIU/mL = 1 IU/L

Is a change real?

FSH naturally varies about 8% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 25% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: The European biological variation study (EuBIVAS): Biological variation data for testosterone, follicle stimulating hormone, prolactin, luteinizing hormone and dehydroepiandrosterone sulfate in men (Itkonen O et al.; corrigendum 2024;559:119720).

For clinicians and researchers

FSH is a heterodimeric glycoprotein with an α subunit shared with LH, TSH and hCG and a hormone-specific β subunit. It is released in pulses by pituitary gonadotropes under GnRH control, with negative feedback from estradiol, inhibin and testosterone. It drives follicle growth in women and spermatogenesis in men. Intervals differ between labs even on the same platform: Labcorp and ARUP (Roche ECLIA) print 1.5–12.4 IU/L for men, while Mayo (also Roche ECLIA) prints 1.2–15.8, and their postmenopausal intervals are 25.8–134.8 and 16.0–157.0 IU/L. Pediatric intervals differ even more between these labs. Thresholds differ by purpose. STRAW+10 treats a random FSH above 25 IU/L (about 40 IU/L in the older urinary standards) as characteristic of the late menopausal transition and says the cutoff depends on the assay. The 2024 ESHRE/ASRM/CREWHIRL/IMS guideline uses at least 4 months of disordered cycles plus FSH above 25 IU/L for premature ovarian insufficiency, repeated after 4 to 6 weeks only if there is diagnostic uncertainty and not timed to a cycle day, and notes that hormonal contraceptives can lower FSH. NICE NG23 advises two samples 4 to 6 weeks apart to identify premature ovarian insufficiency in people under 40, suggests considering FSH to confirm menopause only at ages 40 to 45 with symptoms or under 40 when menopause is suspected, and advises against using FSH to identify menopause in people on combined hormonal contraception or high-dose progestogen. Mayo's comment gives postmenopausal FSH as generally above 40 IU/L. In men, raised FSH and LH point to primary testicular failure, while low or inappropriately normal values with low testosterone point to a pituitary or hypothalamic cause. In PCOS, FSH is typically normal or decreased.

LOINC 15067-2 (primary), 83098-4. Specimen: serum.

Sources

  1. Follicle-stimulating Hormone (FSH) (test 004309), Labcorp
  2. Follicle Stimulating Hormone, Serum (test 0070055), ARUP Laboratories
  3. FSH - Follicle-Stimulating Hormone (FSH), Serum, Mayo Clinic Laboratories
  4. Executive summary of the Stages of Reproductive Aging Workshop + 10, Journal of Clinical Endocrinology & Metabolism (2012)
  5. Evidence-based guideline: premature ovarian insufficiency, ESHRE, ASRM, CREWHIRL and IMS (Human Reproduction Open) (2024)
  6. Menopause: identification and management (NG23), National Institute for Health and Care Excellence (NICE)
  7. Follicle-Stimulating Hormone (FSH) Levels Test, MedlinePlus (NIH)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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