What is FSH? Follicle-stimulating hormone explained
FSH stands for follicle-stimulating hormone. It is one of two hormones, with LH, that link the brain to the ovaries.
FSH only
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What FSH does
MedlinePlus says FSH plays an important role in sexual development in children and fertility in adults. In women who menstruate, FSH helps control the menstrual cycle. It triggers the growth of eggs in the ovaries and gets the eggs ready for ovulation, when an ovary releases an egg.
In men, FSH helps control how much sperm the testicles make. In girls, FSH tells the ovaries to start making estrogen at puberty.
Where it comes from
FSH levels are controlled by a system of hormones made in different parts of the body. MedlinePlus lists three parts:
- the pituitary gland, a small gland at the base of the brain, which makes FSH
- the hypothalamus, a part of the brain that tells the pituitary how much to make
- the ovaries or testicles, whose sex hormone output tells the brain when to start and stop
Abnormal FSH levels may be a sign of a problem with any of these parts.
FSH and menopause
The FDA’s consumer page explains that FSH levels increase temporarily each month to stimulate the ovaries to produce eggs. When you enter menopause and your ovaries stop working, your FSH levels also increase. MedlinePlus puts it this way: as the ovaries release fewer eggs, the body makes more hormones to try to trigger ovulation.
That is why FSH shows up in menopause questions. It is also why one result does not give a diagnosis. See the perimenopause test page for what guidance says.
When FSH is tested
MedlinePlus says an FSH test may be used for women to help find the cause of infertility, check for conditions that affect how the ovaries work, find the reason for irregular or stopped periods, and find out if menopause or perimenopause may have begun. It can also help diagnose disorders of the pituitary gland or hypothalamus. In children and teens it is used to find out if early or late puberty has a medical cause.
It is often done together with LH. Read about the test on the FSH test page, the published ranges on the FSH levels page, and the companion hormone on what is LH.
The FSH-only blood test is the cheapest way to see your number. The seller’s page says it measures FSH only, with no LH, estradiol or testosterone. If you also want LH, you can order the two together.
Sold by HealthLabs. Prices checked October 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.
What a test can’t tell you
An FSH number by itself doesn’t diagnose a condition. Your clinician reads it with your age, symptoms and other hormone results. If your periods have changed or stopped, or you might be pregnant, see a clinician.
FSH only
$49
See this test at HealthLabsPrice checked October 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.
Keep reading
- FSH test: what it measures, why it's ordered and how to prepare
An FSH test measures follicle-stimulating hormone in blood. See why it is ordered, how cycle timing matters, what results can mean and what it can't tell you.
- FSH levels: published reference ranges by cycle phase
FSH reference ranges by cycle phase and after menopause from one named hospital lab, plus what high and low FSH can mean and why your lab's range is the one to use.
- What is LH? Luteinizing hormone, ovulation and blood levels
LH is the pituitary hormone that triggers ovulation. See what it does, how LH ovulation strips differ from a blood test, and one lab's published LH ranges.
- LH and FSH test: why they're tested together and what the ratio means
LH and FSH are usually tested together. See why, when the LH:FSH ratio is used in PCOS questions, how cycle day matters, and one lab's published ranges.