Follicle-stimulating hormone, FSH

What is FSH?

FSH is a hormone associated with reproduction – the development of eggs in women and sperm in men. This test measures blood levels of FSH.

Why Test FSH?

Women who are having difficulties getting pregnant and their partners may have their FSH tested.

Menstrual difficulties
FSH can also be valuable for women who are having irregular or absence of menstrual periods.

Other symptoms
Men who have a low sperm count, low muscle mass, or decreased sex drive and people with symptoms of a pituitary disorder or hypothalamic disorder may have their FSH tested.

What do the results mean?
The meaning of the results varies depending on age and gender.

What causes low FSH?
FSH results are interpreted according to your gender, and age. Your FSH levels are lower than expected for a menstruating woman of your age.

If you are a woman, low FSH levels may mean:

  • Your ovaries are not making enough eggs
  • Your pituitary gland is not working correctly
  • You have a problem with your hypothalamus, a part of the brain that controls the pituitary gland
  • You are underweight

If you are a man, low FSH levels may mean you have a disorder of the pituitary gland or hypothalamus. Low FSH and luteinizing hormone levels in children may be a sign of delayed puberty. Delayed puberty may be caused by:

  • Ovarian or testicle disorder
  • Turner syndrome in girls
  • Klinefelter syndrome in boys
  • An infection
  • A hormone deficiency
  • An eating disorder

What causes high FSH?

Your FSH levels are higher than expected for a menstruating woman of your age. FSH tests are interpreted according to your gender and age.

In women, high FSH levels often correlate with low estrogen and may mean that you have:

  • Primary ovarian insufficiency (POI), is also known as premature ovarian failure. POI is the loss of ovarian function before the age of 40.
  • Polycystic ovary syndrome(PCOS), is a common hormonal disorder affecting childbearing women. It is one of the leading causes of female infertility.
  • Perimenopausal or menopausal naturally have higher FSH levels. In postmenopausal women, chronically high FSH levels are associated with an increased risk of osteoporosis, but also a reduced incidence of type 2 diabetes.
  • An ovarian tumour
  • Turner syndrome, is a genetic disorder that affects sexual development in females and often causes infertility

If you are a man, high FSH levels may mean:

  • Your testicles have been damaged due to chemotherapy, radiation, infection, alcohol abuse, or other reasons for low production of testosterone
  • You have Klinefelter syndrome, a genetic disorder that affects sexual development in males. It often causes infertility

In children, high FSH levels, along with high levels of luteinizing hormone, may mean puberty is about to start or has already started. If this is happening before age 9 in a girl or before age 10 in a boy (precocious puberty), it may be a sign of:

  • A disorder of the central nervous system
  • A brain injury


Follow your health practitioner’s guidance on the correct day to take this test. No other preparation is needed for this test.

If the purpose is to evaluate your fertility, this test should be taken on day 3 (or at least between days 2-5). A woman’s menstrual cycle is measured from the first day of her period (blood flow, not spotting), so Cycle Day 3 is the third day of her period.

On the day of the test
Remember to take I.D. with you when going to take a test.

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