FSH and the FSH test
Also called follicle stimulating hormone, fsh blood test
Reviewed August 2026 against NHS, NIH and WHO references.
In short
Follicle-stimulating hormone, or FSH, is made by the pituitary gland to prompt the ovaries each cycle. As the ovaries wind down, FSH rises, so a blood test can show it is high. But levels swing in perimenopause, so a single FSH test rarely confirms the stage, especially over 45.
What FSH is
Follicle-stimulating hormone is released by the pituitary gland in the brain to tell the ovaries to prepare an egg each cycle. When the ovaries are winding down and responding less, the brain sends more FSH to try to get a result, so the level in the blood rises. A high FSH is therefore a sign the ovaries are slowing.
Why one test rarely settles it
The catch is timing. In perimenopause, FSH does not climb steadily; it swings from high to normal and back, sometimes within the same month. So a single blood test can look 'menopausal' one week and 'normal' the next. For women over 45 with typical symptoms, guidelines generally advise diagnosing from the pattern of periods and symptoms rather than from FSH.
When it is actually useful
An FSH test earns its place when symptoms start young, under 40 to 45, or when the picture is confusing, for example after a hysterectomy that left the ovaries. There it helps assess whether the ovaries are failing early. Your clinician decides whether and when to test, and how to read it alongside everything else.
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This definition is for general information only and is not medical advice. Menopause care depends on your individual health history. Please talk to a qualified clinician about what is right for you.