The LH blood test measures the amount of luteinizing hormone (LH) in blood. LH is a hormone released by the pituitary gland, located on the underside of the brain.
How the Test is Performed
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
How to Prepare for the Test
Your health care provider will ask you to temporarily stop medicines that may affect the test results. Be sure to tell your provider about all the medicines you take. These include:
- Birth control pills
- Hormone therapy
- DHEA (a supplement)
If you are a woman of childbearing age, the test may need to be done on a specific day of your menstrual cycle. Tell your provider if you have recently been exposed to radioisotopes, such as during a nuclear medicine test.
Normal results for adult women are:
- Before menopause - 5 to 25 IU/L
- Level peaks even higher around the middle of the menstrual cycle
- Level then becomes higher after menopause - 14.2 to 52.3 IU/L
LH levels are normally low during childhood.
Normal result for men over 18 years of age is around 1.8 to 8.6 IU/L.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test result.
Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
What Abnormal Results Mean
In women, a higher than normal level of LH is seen:
- When women of childbearing age are not ovulating
- When there is an imbalance of female sex hormones (such as with polycystic ovary syndrome)
- During or after menopause
- Turner syndrome (rare genetic condition in which a female does not have the usual pair of 2 X chromosomes)
- When the ovaries produce little or no hormones (ovarian hypofunction)
In men, a higher than normal level of LH may be due to:
- Absence of testes or testes that do not function (anorchia)
- Problem with genes, such as Klinefelter syndrome
- Endocrine glands that are overactive or form a tumor (multiple endocrine neoplasia)
In children, a higher than normal level is seen in early (precocious) puberty.
A lower than normal level of LH may be due to the pituitary gland not making enough hormone (hypopituitarism).
Why the Test is Performed
In women, an increase in LH level at mid-cycle causes release of eggs (ovulation). Your doctor will order this test to see if:
- You are ovulating, when you are having trouble getting pregnant or have periods that are not regular
- You have reached menopause
If you are a man, the test may be ordered if you have signs of infertility or lowered sex drive. The test may be ordered if you have signs of a pituitary gland problem.
Chernecky CC, Berger BJ. Luteinizing hormone - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:743-744.
Jeelani R, Bluth MH. Reproductive function and pregnancy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 25.