LH blood test measures the amount of luteinizing hormone (LH).

LH is a protein hormone released by the anterior pituitary gland. In women, an increase in LH levels at mid-cycle causes ovulation.

In men, LH stimulates production of testosterone.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

The health care provider may advise you to avoid drugs that may affect the test. Drugs that can decrease LH measurements include birth control pills, hormone replacement therapy, and testosterone.

If you are a woman of childbearing age, the test may need to be done on a specific day of your menstrual cycle.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Your doctor may order this test if you are having trouble getting pregnant or have signs of a disorder associated with abnormal levels of LH.

• Adult male: 7 to 24 international units per liter (IU/L)
• Adult female: 5 to 20 IU/L (levels peak around the middle of the menstrual cycle)

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Greater-than-normal levels of LH may indicate:

• Anorchia (absence of testes or testes that do not function)
• Hypogonadism
• Klinefelter syndrome
• Menopause
• Ovarian failure (see Ovarian hypofunction)
• Polycystic ovary disease
• Precocious puberty
• Turner syndrome

Lower-than-normal levels of LH may indicate hypopituitarism.

Additional conditions under which the test may be performed include:

• Anovulatory bleeding
• Infertility
• Multiple endocrine neoplasia (MEN) I
• Ovarian cysts

Veins and arteries vary in size from one patient 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 light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Recent exposure to radioisotopes (a recent nuclear medicine scan, for example) can interfere with test results.