A follicle-stimulating hormone test measures the amount of follicle-stimulating hormone (FSH) in a blood sample. FSH is produced by the pituitary gland.

• In women, FSH helps control the menstrual cycle and the production of eggs by the ovaries. The amount of FSH varies throughout a woman's menstrual cycle and is highest just before she releases an egg (ovulates).
• In men, FSH helps control the production of sperm. The amount of FSH in men normally remains constant.

The amounts of FSH and other hormones (luteinizing hormone, estrogen, and progesterone) are measured in both a man and a woman to determine why the couple cannot become pregnant (infertility). The FSH level can help determine whether male or female sex organs (testicles or ovaries) are functioning properly.

Why It Is Done

A follicle-stimulating hormone (FSH) test may be done to:

• Help find the cause of infertility. FSH testing is commonly used to help evaluate a:
  • Woman's egg supply (ovarian reserve).
  • Man's low sperm count.
• Help evaluate menstrual problems, such as irregular or absent menstrual periods (amenorrhea). This can help determine whether the woman has gone through menopause.
• Determine whether a child is going through early puberty (also called precocious puberty). Puberty is early when it starts in girls younger than age 9 and in boys younger than age 10.
• Determine why sexual features or organs are not developing when they should (delayed puberty).
• Help diagnose certain pituitary gland disorders, such as a tumor.

How To Prepare

Many medicines, such as cimetidine, clomiphene, digitalis, and levodopa, can change your test results. You may be asked to stop taking medicines (including birth control pills) that contain estrogen or progesterone or both for up to 4 weeks before having a follicle-stimulating hormone (FSH) test. Make sure your health professional has a complete list of all the prescription and over-the-counter medicines you are taking, including herbs and natural substances.

Tell your health professional if you have had a test that used a radioactive substance (tracer) within the last 7 days. Recent tests using a radioactive tracer (such as a thyroid scan or bone scan) can interfere with FSH test results.

Let your health professional know the first day of your last menstrual period. If your bleeding pattern is light or begins with spotting, the first day is the day of heaviest bleeding.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

The health professional drawing your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

For a woman who is having problems with her menstrual cycle or who cannot become pregnant, more than one blood sample may be needed to help identify a follicle-stimulating hormone (FSH) problem. A sample may be taken each day for several days in a row.