LH (luteinizing hormone)
Pituitary hormone that controls ovulation and testosterone production
Also known as
Definition
LH is a hormone made by the pituitary gland. In women, it helps control the menstrual cycle and triggers ovulation. In men, it prompts the testicles to make testosterone, which is needed for sperm production. In children, LH rises before puberty. It is usually measured together with FSH and helps doctors assess disorders of the ovaries, the testicles, or the pituitary gland and hypothalamus.
| Parameter | Value |
|---|---|
| Unit | IU/l (equivalent to mIU/ml) |
| Reference Range | There is no single range: LH depends on sex and age and, in women, on the phase of the cycle. It rises quickly just before ovulation, is often higher around menopause, is normally low in early childhood and changes little in men. Labs set their own reference ranges; the range on your own report is what counts. Discuss deviations with your doctor. |
Agree on your personal target range with your doctor.
1 IU/l equals 1 mIU/ml; the numbers are identical in both units.
↓ What a low value means
A low LH level can be linked to a problem with the pituitary gland or hypothalamus that makes it hard for the body to produce enough LH and FSH. In women with missed periods, low LH and FSH levels can also be linked to extreme exercise, malnutrition, stress or being very underweight. A single value is not a diagnosis; discuss the result with your doctor.
↑ What a high value means
In women of childbearing age, a level that stays high throughout the cycle can be linked to ovarian dysfunction, such as ovaries that did not develop normally, primary ovarian insufficiency, polycystic ovary syndrome (PCOS), thyroid or adrenal disorders, or Turner syndrome. From about age 45, it can point to approaching menopause. In men, a high level can be linked to mumps, injury to or abnormal development of the testicles, a germ cell tumor or Klinefelter syndrome; in both sexes also to damage from autoimmune disease, radiation or chemotherapy. In children, it can be linked to early puberty. Discuss the result with your doctor.
When to test
LH is measured, for example, when pregnancy has not occurred after twelve months of trying, with irregular or missed periods, when early or premature menopause is suspected, with low testosterone, reduced libido or a low sperm count, and with early or delayed puberty. Women with a cycle may be asked to test on a specific cycle day. Certain medicines and supplements can affect the result; mention everything you take, but do not stop anything on your own.
Frequently asked questions
Why are LH and FSH usually measured together? +
Both hormones come from the pituitary gland and jointly control how the ovaries and testicles work. Doctors therefore usually look at them together, often alongside estradiol or testosterone.
Why does LH vary so much in women? +
LH changes over the menstrual cycle and rises quickly just before ovulation; this surge triggers ovulation. Around menopause the level is often higher. That is why the blood draw may need to be done on a specific cycle day.
Can medicines or supplements affect LH? +
Yes. Certain medicines and supplements can change the result. Mention everything you take before the blood draw and do not stop anything without talking to your doctor.
Are IU/l and mIU/ml the same? +
Yes. 1 IU/l equals 1 mIU/ml, so the number stays the same. Reference ranges can still differ between labs; the range on your own report is what counts.
LH (luteinizing hormone)
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.