Finding the right tests…
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Finding the right tests…
Hormonal
Luteinizing hormone, or LH, is released by your pituitary gland, a small gland at the base of your brain, and it triggers ovulation in women while driving testosterone production in men. Your doctor checks LH when periods have stopped or turned irregular, when a couple has been trying to conceive without success, or when puberty seems to be starting too early or too late. In men, the same test looks at whether the testicles are getting the pituitary signal they need to make testosterone. Because LH surges sharply just before ovulation, when in your cycle the blood is drawn changes what the result actually means.
This test reports the amount of LH in your blood, in international units per litre. In women, a single value only means something in the context of your cycle, since LH rises and falls through the month and surges sharply just before ovulation — it's sometimes checked on several days to catch that surge. In men, one sample is usually enough, since LH runs at a steadier level day to day. The lab compares your result against separate ranges for men, premenopausal women, and postmenopausal women, since a level expected after menopause would look unusually high at any other stage.
LH works together with follicle-stimulating hormone (FSH) to drive the reproductive cycle. In women, LH stays low for most of the month until a sharp surge about two weeks before your period, which triggers the ovary to release an egg — the same surge that home ovulation kits are designed to detect. In men, LH signals the testicles to keep producing testosterone, working at a steadier pace rather than in a monthly cycle.
In women, a high LH level can point to polycystic ovary syndrome, reduced ovarian function, or the approach of menopause, when LH rises because the ovaries respond less to signals from the brain. In men, a high LH alongside low testosterone suggests the testicles aren't responding properly, which can follow injury, infection, or a genetic condition such as Klinefelter syndrome.
A low LH level in either sex points toward the pituitary gland or hypothalamus rather than the ovaries or testicles. In women, this pattern can also appear with very low body weight, heavy exercise, or significant stress, since all three can suppress the signal from the brain before it reaches the ovaries.
LH is rarely read alone. Your doctor usually looks at it next to FSH, estrogen, or testosterone results to build the full picture rather than deciding from one number.
For men over 18, a normal LH level is generally 1.8 to 8.6 IU/L, based on MedlinePlus reference values. Ranges vary by lab, so check the figures printed on your own report.
It can point to polycystic ovary syndrome, reduced ovarian function, or early menopause, since LH rises when the ovaries respond less to signals from the brain. Your doctor will look at it alongside other hormone levels and your symptoms before drawing any conclusion.
It can show that a surge is happening, since LH spikes sharply about a day or two before ovulation, the same principle home ovulation predictor kits use. A single lab draw is less practical for real-time tracking than urine kits, so doctors typically use it to confirm ovulation happened rather than catch the surge live.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
LH and FSH work together to control the reproductive cycle, so reading them side by side gives a clearer picture than either alone. A pattern where both are high, for instance, points toward the ovaries or testicles, while both being low points toward the pituitary gland.
No special fasting is needed for this test. Your doctor may still ask you to have it drawn on a specific day of your menstrual cycle, since the result depends on timing.
No — LH rises naturally after menopause, to roughly 7.7 to 58.5 IU/L in the usual reference range, because the ovaries stop responding to the pituitary's signal. Your doctor reads a postmenopausal result against that higher range, not the premenopausal one.
Yes. In women, significant stress, very low body weight, or heavy exercise can suppress LH by affecting the signal from the brain to the ovaries. Tell your doctor about any of these if you're being tested for irregular periods.