Luteinizing Hormone (LH) Blood Test

Written by Mary Ellen Ellis | Published on July 18, 2012
Medically Reviewed by George Krucik, MD

Overview

Luteinizing hormone (LH) is an important hormone produced in both men and women. It plays a role in puberty, menstruation, and fertility. Your doctor may request a test of your LH levels if you display certain symptoms, such as:

  • inability to become pregnant
  • irregular or missed periods
  • early signs of puberty
  • delayed puberty

Knowing the amount of LH in your blood can indicate underlying problems associated with a variety of reproductive health issues.

What Is Luteinizing Hormone?

LH is a hormone that is produced in the pituitary gland in both men and women. In women, LH is an important part of the menstrual cycle. It works in conjunction with follicle-stimulating hormone (FSH), also made in the pituitary gland. FSH stimulates the ovarian follicle causing an egg to grow. It also triggers the production of estrogen in the follicle.

The rise in estrogen tells the pituitary gland to stop producing FSH and to start making more LH. The shift to LH causes the egg to be released from the ovary, a process called ovulation. In the empty follicle, cells proliferate, turning it into a corpus luteum. This structure releases progesterone, a hormone necessary to maintain pregnancy. If pregnancy does not occur, levels of progesterone drop off and the cycle begins again.

In men, LH is also produced in the pituitary gland. LH binds to receptors in certain cells in the testes called Leydig cells. This leads to the release of testosterone, a hormone that is necessary for producing sperm cells.

What Is a Luteinizing Hormone Blood Test?

An LH blood test is a measurement of the amount of the hormone in your bloodstream. The amount of LH in a woman’s bloodstream varies throughout the menstrual cycle and changes with pregnancy. LH levels can also be measured by analyzing a urine sample.

What Are the Reasons for Requesting a Luteinizing Hormone Blood Test?

There are many reasons for your doctor to request a blood level test of luteinizing hormone. Levels of LH relate to menstrual issues, fertility, and the onset of puberty.

Menstrual Cycle and Menopause

If you have absent or irregular periods, your doctor may want to examine the amount of LH in your bloodstream in order to find an underlying cause. A change in the amount of LH can indicate the onset of menopause.

Fertility

Your doctor may order an LH blood test if you are having difficulty conceiving. LH levels can indicate the supply of eggs in a woman’s ovaries and a man’s sperm count, both of which affect fertility.

Puberty

For a younger patient, a doctor may order an LH blood test to find the underlying causes for delayed or early puberty.

Pregnancy

A test of LH levels in the urine can be used to determine when a woman is ovulating. These types of tests can be done at home and are often used to enhance the chances of conceiving.

How Is the Test Administered?

To administer an LH blood test, a health professional will draw a small amount of blood from you, most likely from your arm. The short procedure will be done in your doctor’s office or in a lab in the building. The sample will then be analyzed for LH levels.

To draw blood, a nurse or phlebotomist will wrap your upper arm with an elastic band to make your veins easier to see. They will disinfect the skin and then insert a needle into a vein on the inside of your arm. A tube attached to the needle will collect a small sample of your blood. The process is short and mostly painless.

Your doctor may request that you have samples of blood drawn each day for several days. Because the amount of LH in the blood varies with your menstrual cycle, a few samples may be necessary to get an accurate measurement of your LH levels.

What Are the Risks Associated With a Luteinizing Hormone Blood Test?

There are not many risks involved when having blood drawn. The needle site may bruise afterwards, but if you put pressure on it with a bandage, you can reduce this possibility. Phlebitis, while rare, may occur when blood is drawn. This is when the vein becomes inflamed after blood is taken. If it occurs, your healthcare provider will likely have you apply a warm compress to the vein throughout the day. If you have any kind of bleeding disorder, you should tell your doctor to avoid complications from having blood drawn.

How Should I Prepare for a Luteinizing Hormone Blood Test?

Your doctor should give you exact directions to prepare for your blood test. You may be told to stop taking certain medications that can affect the results, so be sure to inform your doctor of all medications and supplements you take. You may need to stop taking birth control or other hormone pills for up to four weeks before the test. Your doctor will also want to know the date of your last period.

As with many blood draws, you may be asked to avoid eating or drinking for up to eight hours leading up to the test.

If you have had any type of test or procedure with a radioactive substance seven days before the LH blood test, your doctor will need to know. These substances can interfere with the results of your test.

Understanding the Results of an LH Test

Your doctor can tell you when results of your test will be available and will discuss the meaning of your levels with you. Below are normal LH blood levels according to the Department of Pathology and Laboratory Medicine at the University of California, San Francisco. The units are international units per liter (IU/L):

  • women in the follicular phase of the menstrual cycle: 1.9 to 12.5 IU/L
  • women at the peak of the menstrual cycle: 8.7 to 76.3 IU/L
  • women in the luteal phase of the menstrual cycle: 0.5 to 16.9 IU/L
  • pregnant women: less than 1.5 IU/L
  • women past menopause: 15.9 to 54.0 IU/L
  • women using contraceptives: 0.7 to 5.6 IU/L
  • men between the ages of 20 and 70: 0.7 to 7.9 IU/L
  • men over 70: 3.1 to 34 IU/L

Your doctor will help you understand your results, what they mean, and what steps you should take next. In general, higher than normal levels of LH in a woman may mean the ovaries are absent or not functioning. In a young woman, high levels may mean that puberty is early. In men, high levels may mean that the testicles are not functioning or have been removed, or it can indicate the presence of Klinefelter syndrome (a genetic condition affecting sexual development in males).

Low levels of LH in the blood may indicate anorexia, an issue in the pituitary gland, stress, or damage to the hypothalamus in both men and women.

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