Follicle-stimulating hormone (FSH) supports estrogen production and reproductive processes in your body. Because FSH regulates both ovulation and sperm production, this hormone is often tested to check someone’s fertility.

FSH levels rise as you age. If your periods have become irregular and you have questions about menopause, your doctor may recommend FSH testing to gather more information on your hormone activity.

Menopause can’t be confirmed based on a single test, but FSH is an important piece of the puzzle.

Read on to learn about FSH, menopause, and what you can expect from an FSH test.

FSH is a hormone released by the pituitary gland into the bloodstream.

Along with LH (luteinizing hormone), FSH is a gonadotropin. Gonadotropic hormones stimulate the gonads, or reproductive organs. They’re necessary for puberty to start.

FSH is needed for ovarian and testicular function. FSH supports the ovaries to make estrogen and the testes to make testosterone. Without FSH, ovaries can’t produce eggs and testes can’t produce sperm.

How FSH works in the body

FSH production begins in a part of the brain called the hypothalamus, located at the base of the brain next to your pituitary gland.

These are the typical stages of FSH production:

  1. The hypothalamus delivers gonadotrophin-releasing hormone to the pituitary gland.
  2. This signals the pituitary gland to produce and release FSH and LH into the bloodstream.
  3. FSH travels through the blood to the reproductive organs, where it binds to receptors in the testes or ovaries.

Here’s a simplified overview of how FSH works for ovulation and menstruation:

  1. During the first half of the menstrual cycle, FSH secretion rises.
  2. The presence of high levels of FSH and LH stimulates the ovaries to release a follicle, which contains an egg.
  3. The follicle also begins to produce estrogen, so FSH production stops.
  4. When the follicle matures, the egg is released, and ovulation occurs.
  5. A temporary structure called the corpus luteum forms around the empty follicle. Its job is to pump out hormones to support pregnancy.
  6. If fertilization does not occur after ovulation, the corpus luteum falls apart, causing estrogen levels to drop.
  7. Menstruation is triggered.
  8. The process of producing FSH begins again.

FSH isn’t the only hormone in this reproductive process. LH, estrogen, and progesterone also play important roles.

Ovulation and menstruation occur monthly in many people during their main reproductive years. This process tapers off during perimenopause, the transitional stage that happens before menopause.

According to the National Institute on Aging, menopause usually occurs between the ages of 45 and 55. It can last anywhere from 7 to 14 years. You’ve reached menopause when it’s been at least 12 months since your last period.

Menopause is not a disorder. It is a natural process where the number of follicles in the ovaries quickly reduces. Since these follicles produce estrogen, as they decline, so does your estrogen production.

Lower estrogen levels create a feedback loop. Your brain signals to produce more FSH to stimulate the follicles. But there aren’t enough follicles to use the FSH, raising FSH levels in your bloodstream. Eventually, the reduced supply estrogen for the menstruation process causes menstruation to stop.

Even after menopause, your body continues to produce estrogen in smaller amounts, converted from the testosterone released by your adrenal glands. The extent of menopause symptoms varies widely depending on the individual.

FSH and other health conditions

In addition to menopause testing, FSH measurement can be used to diagnose health conditions that affect fertility.

These include:

The FSH test is a simple blood test measured in milli-international units per milliliter (mIU/mL) or in international units per liter (IU/L).

Like any blood test, an FSH test has minimal to no risks. You may experience slight pain from the needle going into your skin, and some temporary bruising at the injection site.

Understanding FSH results

It’s hard to pinpoint a specific range for “normal” FSH levels. FSH level testing often involves looking at how levels fluctuate or change in the individual, and evaluating any symptoms they’re experiencing. What is considered the average range for FSH also may vary slightly depending on your doctor, lab, and brand of test being used. FSH ranges also very by your age (prepubescent, during and after puberty, postmenopausal).

As a 2003 research article explains, especially for pre-menopausal people, “a single determination is insufficient to reliably estimate a woman’s true average serum FSH level and repeated measurements are desirable.”

According to The North American Menopause Society, when someone hasn’t had a menstrual period in a year or longer and has FSH levels “consistently elevated to 30 mIU/mL or higher,” doctors often agree menopause has been reached.

Here’s a general idea of how FSH is measured for most women. The Mount Sinai Healthcare System cites the following ranges, but again, these may vary by hospital:

Age groupNormal FSH level range
before puberty0–4.0 IU/L
during puberty0.3–10.0 IU/L
while still menstruating4.7–21.5 IU/L
after menopause25.8–134.8 IU/L

FSH levels can rise and fall, especially during perimenopause. For this reason, your doctor may recommend monthly testing, especially if you are trying to become pregnant. In this instance, they’ll use your highest FSH level as a marker to determine your fertility potential.

If you were assigned female at birth but are on hormone treatment, such as puberty blockers or testosterone, these FSH numbers may not apply to you. If you are worried about menstruation changes, ovarian pain, or hormone levels, consult with your doctor. They can provide an individualized approach to your care.

FSH testing is a routine part of the fertility or infertility checkup. It may also be done in extreme athletes or people with possible eating disorders who are menstruating irregularly or not at all.

According to the Office on Women’s Health, periods are considered irregular if the number of days between periods is less than 21 or greater than 35. Pregnancy is a major reason for changes in menstruation. If this is ruled out, FSH testing may be the next step.

If you have irregular periods or vaginal bleeding between periods, your doctor may recommend FSH testing and use other diagnostic tools, such as sonograms.

You may also wish to get medical input if you’re experiencing the hallmark symptoms of menopause. These can be uncomfortable and affect daily life.

Signs of menopause include:

FSH is an essential hormone. It’s involved in several key reproductive functions, including ovulation. Doctors use FSH level tests to identify possible perimenopause, menopause, and fertility issues, such as PCOS and POI. FSH test results alone cannot diagnose menopause, but they are an important tool.

The FSH test is a simple blood test. Multiple tests may be needed to get the full picture, or tests may be taken at different points in the hormone cycle. If you are experiencing menopause, your FSH level will likely be over 25.8 IU/L.

Menopause is a naturally occurring biological process that affects billions of people! It often begins after age 45.

If you’re experiencing menopause symptoms, including sweats and irregular menstruation, reach out to your doctor. An FSH test may be able to help your doctor identify menopause or another health condition.