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Blood Test Tracker

Luteinizing Hormone (LH)

A pituitary hormone that triggers ovulation in women and tells the testes to make testosterone in men. It surges mid-cycle.

AI-verified against cited sources. Awaiting expert reviewAlso called LH, ICSHLOINC 10501-5

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The usual range for LH depends on sex. Choose female or male above to see where you stand.

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What it is

Luteinizing hormone (LH) is made by the pituitary gland and works as a partner to FSH. In women, a sharp rise in LH in the middle of the cycle causes the ovary to release an egg (ovulation). In men, LH tells the testes to make testosterone. LH is released in pulses, so a single blood result can be higher or lower than your average.

Why it matters

LH is usually checked together with FSH, estradiol and sometimes testosterone. It helps clinicians look into missed or irregular periods, fertility questions, low testosterone in men, and puberty that starts very early or late. Home urine kits that track ovulation measure LH. Because LH moves a lot through the cycle and through the day, the cycle day and the other hormones matter when reading one result.

If it’s low

A low LH can mean the pituitary, or the part of the brain that signals it, is sending a weaker signal. It's also seen with hormone medicines, low body weight, very heavy exercise and stress, and many of these causes are temporary. In men, a low LH together with low testosterone can point to the pituitary or the brain rather than the testes.

Common causes

  • Hormonal birth control, or estrogen or testosterone treatment, including anabolic steroids
  • Low body weight, not eating enough, very heavy exercise or severe stress
  • A problem with the pituitary gland or the hypothalamus, including tumors
  • Inherited conditions such as Kallmann syndrome
  • Late puberty that is a normal variation in some teens

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 LH is expected at the mid-cycle surge and after menopause. Outside of those times, it can mean the ovaries or testes aren't responding well to LH's signal, or it can be seen with polycystic ovary syndrome. A clinician will look at your cycle, symptoms and other hormones before drawing any conclusion.

Common causes

  • The normal surge just before ovulation
  • Menopause and perimenopause
  • Polycystic ovary syndrome
  • 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
  • In men, testicular failure
  • In children, puberty that starts earlier than usual

What can help

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

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

If this applies to you

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

Strength training

LH is the brain's signal to the testes to make testosterone. A high testosterone with a suppressed LH and FSH is the pattern seen when testosterone comes from outside the body.

Blood tests for strength training and bodybuilding

Trying to conceive

NICE offers LH and FSH tests when cycles are irregular. ASRM lists LH among the tests not ordered routinely unless there is a specific reason.

Blood tests for trying to conceive, including IVF

On testosterone therapy

LH is mostly measured before treatment, together with FSH, to help tell whether low testosterone comes from the testes or from the pituitary, the Endocrine Society says. It also notes that biotin supplements can throw off LH and FSH tests.

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

What can affect your result

  • Menstrual cycle day: LH is lowest in the early and later phases and surges briefly around ovulation
  • 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.
  • Hormonal birth control, estrogen or testosterone treatment and other hormone medicines can lower LH, so the result may not show what your body does on its own.
  • LH is released in pulses, so one sample may not match your average level. Labcorp notes that pooling equal amounts of blood drawn 15 to 30 minutes apart has been suggested.
  • People treated with mouse monoclonal antibodies, or who had them for imaging, can get erroneous results with some assays.
  • hCG, the pregnancy hormone, is built very much like LH. Mayo reports no clinically significant cross-reactivity with hCG for its assay, but tell the person ordering the test if you could be pregnant or are having fertility treatment.

Any time of day, but LH is released in pulses and changes through the cycle, so ask which cycle day your clinician wants. To catch the mid-cycle surge, home urine ovulation kits are used more often than blood tests. Reflects the current feedback between the brain and the ovaries or testes. In women it changes from day to day around ovulation, so timing matters.

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've been trying to conceive for 12 months without success, or if you're a man with a low sperm count, loss of interest in sex or loss of muscle and body hair. 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, fertility or symptoms?
  • Could my age, cycle day or a medicine explain this result?
  • Should we repeat the test on a specific cycle day?
  • Should we check FSH, estradiol or other hormones too?
  • Could my weight, exercise, stress or a medicine explain this result?

Questions people ask

Is a blood LH test the same as an ovulation test?

They measure the same hormone, but not in the same way. Home ovulation kits measure LH in urine and look for the surge. A blood LH test is a snapshot, so it catches the surge only if the blood happens to be drawn then.

Does LH higher than FSH mean I have PCOS?

Not necessarily. LH and FSH change with the cycle day, and LH can run higher than FSH at mid-cycle for ordinary reasons. A clinician will look at your cycle, your symptoms and other hormones, not one number.

Why can my LH change from one draw to the next?

LH is released in pulses, and in women it changes across the cycle. Blood drawn at a different time of day or cycle day can give a different number. Pooling several samples drawn 15 to 30 minutes apart has been suggested to get a steadier picture.

What does LH do in men?

LH tells the testes to make testosterone. A clinician may check LH with FSH and testosterone when testosterone is low, to help tell whether the cause is in the testes or in the brain's signals.

Is IU/L different from mIU/mL?

No. They are the same number, so 5.0 mIU/mL is the same as 5.0 IU/L and no conversion is needed. Some labs print the unit as U/L.

Show the science and sources

Units

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

Is a change real?

LH naturally varies about 22% from test to test in the same healthy person. Between two results from the same lab, a rise of 96% or more, or a fall of 49% 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

LH is a heterodimeric glycoprotein with an α subunit (92 amino acids) shared with FSH, TSH and hCG and a hormone-specific β subunit of 121 amino acids. It is released in pulses by pituitary gonadotropes under GnRH control. In women it supports ovarian theca-cell androgen production for estradiol synthesis, triggers ovulation at the mid-cycle surge and maintains the corpus luteum. In men it stimulates Leydig-cell testosterone production. The β subunit shares its sequence with hCG-β (which carries an extra 24 amino acids), so hCG cross-reactivity is assay-dependent, and Mayo reports none that is clinically significant for its assay. Intervals differ between labs even on the same platform. Roche ECLIA at Labcorp and ARUP lists 1.7–8.6 IU/L for men and, for women, 2.4–12.6 follicular, 14.0–95.6 mid-cycle, 1.0–11.4 luteal and 7.7–58.5 postmenopausal. Mayo, also on Roche ECLIA, lists 1.3–9.6 for men and 1.9–14.6, 12.2–118.0, 0.7–12.9 and 5.3–65.4 for women, and says postmenopausal LH is generally above 40 IU/L. In men, raised LH with low testosterone points to primary testicular failure, while low or inappropriately normal LH with low testosterone points to a pituitary or hypothalamic cause. Labcorp notes that pulsatile secretion can make one sample hard to interpret and that pooling equal volumes of serum drawn at 15 to 30 minute intervals has been suggested. Biotin and anti-animal (including mouse) antibody interference apply to these immunoassays. Pediatric intervals differ widely between labs (ARUP's are much lower than Labcorp's and Mayo's at ages 7 to 17).

LOINC 10501-5 (primary), 83103-2. Specimen: serum.

Sources

  1. Luteinizing Hormone (LH) (test 004283), Labcorp
  2. Luteinizing Hormone and Follicle Stimulating Hormone (test 0070193), ARUP Laboratories
  3. LH - Luteinizing Hormone (LH), Serum, Mayo Clinic Laboratories
  4. Luteinizing Hormone (LH) 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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