What Is a Luteinizing Hormone Test?
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.
Why Would I Get a Luteinizing Hormone Test?
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:
- Unexplained weight loss
- Decreased appetite
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:
- You’re having trouble getting pregnant
- Your periods aren’t regular
- To see if you are in menopause
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:
- You have a lower sex drive
- You have low testosterone levels
- You have low muscle mass
For children, a doctor might order an LH test if:
- Your child seems to be going through puberty early
- Your child seems to be going through puberty late
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:
- Beginning of menstruation
- Breast development in girls
- Pubic hair
- Growth of penis and testicles
What Happens During a Luteinizing Hormone Test?
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.
Luteinizing Hormone Test Results
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:
- 5-25 international units per liter (IU/L) before menopause
- 14.2-52.3 IU/Ll after menopause
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:
- You have a metabolic disorder, a genetic disorder, like Turner syndrome, or an autoimmune disorder, like Addison disease
- You have a low number of follicles, the tiny sacs in your ovaries
- You’ve gone through chemotherapy or radiation therapy
- You were exposed to toxins like chemicals, pesticides, or smoke from cigarettes in the past
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:
- Are obese
- Had undescended testicles at birth
- Have a disease that affects your testicles, like mumps, testicular cancer, or testicular torsion
- Have a genetic disease or another disease, like cystic fibrosis
- Take certain medicines, like chemotherapy or opioid pain medicines
- Use marijuana often
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:
- An injury to their brain
- A central nervous systems disorder
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:
- An eating disorder
- A disorder of the ovaries or testicles
- A genetic disorder, like Turner syndrome in girls or Klinefelter's syndrome in boys
- A hormone deficiency
- An infection
Your LH level, by itself, isn’t enough to make a diagnosis. So you may get other tests too.