Written by WebMD Editorial Contributors
Medically Reviewed by Carol DerSarkissian, MD on September 05, 2024
A luteinizing hormone test measures how much luteinizing hormone (LH) is in your blood.
LH helps your reproductive system: specifically, a woman’s ovaries and a man’s testes. It’s also called lutropin and interstitial cell stimulating hormone. It’s made in your pituitary gland, which is about the size of a pea and sits just behind your nose.
There are different reasons you might get a luteinizing hormone test. Your doctor might order an LH test as part of an infertility workup or to check for a pituitary gland problem.
Signs of a pituitary gland disorder include:
Other reasons for doing an LH test can differ depending on your sex and sometimes, your age.
An increase in LH during the middle of your cycle causes your ovaries to release eggs (ovulation).
Your doctor might order an LH test if:
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. The amount of LH in your blood surges with ovulation.
There are at-home LH tests that help pinpoint when during your cycle you’re most likely to get pregnant. You can buy these types of tests in drug stores. During the middle of your cycle, you pee on the test stick. If the test is positive, that means there’s an LH surge. This could mean you’ll ovulate within the next day or two, but that might not be the case for everyone. These tests aren’t as accurate as the ones done at a doctor’s office.
For men, your doctor might order an LH test if:
For children, a doctor might order an LH test if:
Low LH levels are linked to late puberty, and high levels are linked to early puberty. Signs of early puberty include these things happening before age 8 in girls and 9 in boys:
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.
Your doctor may also check your level of something called follicle-stimulating hormone – or FSH – at the same time.
Your doctor will probably have the results in a few days.
Normal LH numbers depend on a few things, like your sex and age. For women, normal results are:
The level peaks higher during the middle of your cycle.
For men, the normal levels are around 1.8-8.6 IU/L.
For children, LH levels are generally low.
Keep in mind that the “normal” value ranges can differ depending on the lab, so you should always talk to your doctor about what your result means for you.
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.
Doctors often can’t pinpoint why primary ovarian failure happens. But it can happen if:
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 and can be a sign of primary testicular failure.
Primary testicular failure isn’t common, but it can happen if you:
It can also happen if your testicles are injured or if you do activities that cause low-level injury to your scrotum, like when you ride a bike or a motorcycle.
Low levels of LH mean the issue is with the pituitary gland or hypothalamus.
If your child has high LH levels, it could mean they’re about to go through puberty or that it’s already started. But if they’re a girl younger than 8 years old or a boy younger than 9, it could be a sign of something like:
If your child has low LH levels, they might have delayed puberty, which is where they go through puberty much later than expected. This could happen because of:
Your LH level, by itself, isn’t enough to make a diagnosis. So you may get other tests too.
SOURCES:
Endocrine Society Hormone Health Network: “What Does Luteinizing Hormone Do?”
The Pituitary Foundation:
