What Is a Luteinizing Hormone (LH) Test?

This test measures how much luteinizing hormone (LH) is in your blood.

LH is a hormone that helps your reproductive system: specifically, a woman’s ovaries and a man’s testes. It’s made in your pituitary gland, which is about the size of a pea and sits just behind your nose.

Why Would I Get It?

The main reasons your doctor might order an LH test are:

  • As part of an infertility workup for a woman or a man
  • To check for a pituitary gland problem

Your doctor may also check your level of something called follicle-stimulating hormone – or FSH – at the same time.

Symptoms other than infertility that might prompt your doctor to order this test include:

  • Menstrual periods that don’t happen when they should
  • Periods that don’t show up at all
  • Low testosterone level in a man
  • Low sex drive in a man
  • Low muscle mass in a man

Signs that you could have a pituitary gland disorder include:

If you are trying to become pregnant, your doctor might want you to get an LH test several times to pinpoint when your body releases an egg, which is called ovulation. The amount of LH in your blood surges with ovulation.

Doctors also order the LH test when a boy or girl has not entered puberty as expected, or appears to be entering puberty early. Low levels are linked to late puberty, and high levels are linked to early puberty. Signs of early puberty include:


What Happens?

You don’t need to do anything special to prepare for this test.

The health care worker who takes blood for your test will wipe the inside of your elbow with a germ-killing liquid. You’ll have an elastic band around the upper part of your arm.

To collect the sample for the test, the health care worker inserts a thin needle into a vein in your arm, and the blood flows into a vial. You might feel a sting when the needle goes in.

When the vial is full, the tech or nurse will remove the needle and the tourniquet. You’ll get a bandage to stop the bleeding. The whole thing takes only a few minutes.

You might feel lightheaded after the test. You also might develop a bruise at the puncture site.

What the Results Mean

Your doctor will probably have the results in a few days.

High levels of LH in a woman’s blood can be a sign of what’s called “primary ovarian failure,” which means that the problem is with the ovaries themselves. Low levels of LH may be a sign of “secondary ovarian failure,” which means the problem starts with the pituitary gland or hypothalamus (a part of the brain).

In men, high levels of LH in the blood are a sign of a problem with the testicles. Low levels of LH mean the issue is with the pituitary gland or hypothalmus.

Your LH level, by itself, isn’t enough to make a diagnosis. So you may get other tests, too.

WebMD Medical Reference Reviewed by Nivin Todd, MD on January 30, 2019



Endocrine Society Hormone Health Network: “What Does Luteinizing Hormone Do?”

The Pituitary Foundation: “What Is the Pituitary Gland?”

UCLA Health Library: “Luteinizing Hormone (Blood).”

American Association for Clinical Chemistry: “Lab Tests Online – LH.”

Kid’s Health by the Nemours Foundation: “Blood Test – Luteinizing Hormone (LH).”

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