LH (Luteinising Hormone) is a blood test that measures lh (luteinising hormone) levels in the blood. Normal range: In women, LH is measured on day 2-3 (roughly 2-10 IU/L early follicular) and surges sharply at ovulation to trigger egg release; it rises above ~15-20 IU/L after menopause. In men it is steady at about 1.5-9 IU/L. Exact ranges depend on the lab and assay.. It is commonly used to helps evaluate fertility, reproductive disorders, and hormone imbalances affecting both sexes..
What is LH (Luteinising Hormone)?
A pituitary hormone that triggers ovulation and stimulates testosterone production.
Why is it measured?
Helps evaluate fertility, reproductive disorders, and hormone imbalances affecting both sexes.
Normal Reference Range
In women, LH is measured on day 2-3 (roughly 2-10 IU/L early follicular) and surges sharply at ovulation to trigger egg release; it rises above ~15-20 IU/L after menopause. In men it is steady at about 1.5-9 IU/L. Exact ranges depend on the lab and assay.
Note: Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation.
What Causes High LH?
High LH alongside high FSH indicates primary gonadal failure — menopause or primary ovarian insufficiency in women, and testicular failure in men. A characteristic pattern in PCOS is a raised LH with a high LH-to-FSH ratio (often 2:1 or more). A brief, expected spike occurs mid-cycle in ovulating women as LH surges to release the egg.
What Causes Low LH?
Low LH reflects reduced signalling from the hypothalamus or pituitary (hypogonadotropic hypogonadism). Causes mirror those for low FSH: pituitary tumours or injury, high prolactin, severe stress, low body weight, excessive exercise, and suppression from exogenous testosterone or anabolic steroids. Low LH and FSH together with low sex hormones points to a central (brain) cause.
How Often Should LH Be Tested?
In women, LH is drawn on day 2-3 of the cycle with FSH and oestradiol for fertility or cycle assessment, or to support a PCOS diagnosis. Home ovulation kits detect the mid-cycle LH surge. In men it is part of a hypogonadism work-up. Repeat testing is guided by the clinical question.
Related Blood Markers
LH is interpreted with FSH (the LH:FSH ratio matters in PCOS), oestradiol or testosterone, and prolactin. AMH and antral follicle count add ovarian-reserve context in women.
Key Facts
- •Category: Hormone Health
- •Unit of Measurement: IU/L
- •Test Code: LH
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