What symptoms or concerns might lead a doctor to order an FSH blood test?

If you have irregular periods, unexplained infertility, early or delayed puberty, or a history of ovarian or testicular issues, your clinician may order an FSH test to assess hormone balance and reproductive health.

How should I prepare for an FSH blood draw?

Most FSH tests do not require fasting, but you should avoid medications that affect hormone levels (like birth control pills or steroids) for at least a week before the test, and for women, the test is usually scheduled in the early follicular phase (days 2–5) of the menstrual cycle.

If my FSH result is abnormal, what are the typical next steps?

Your provider may order additional hormone panels (LH, estradiol, testosterone), imaging studies (ultrasound or MRI), or refer you to a reproductive endocrinologist for further evaluation and tailored treatment options.

What do high or low FSH levels indicate about fertility?

Elevated FSH in women often signals reduced ovarian reserve or early menopause, while low FSH may point to pituitary or hypothalamic dysfunction. In men, high FSH can suggest testicular failure or impaired sperm production, whereas low levels may indicate central hormonal issues.

Follicle-Stimulating Hormone (FSH) Levels Test

The follicle-stimulating hormone (FSH) levels test measures a key hormone in your blood that regulates sexual development in children and fertility in adults.

What is a follicle-stimulating hormone (FSH) levels test?

This test measures the level of follicle-stimulating hormone (FSH) in a sample of your blood. A hormone is a chemical messenger in your bloodstream that controls the actions of certain cells or organs. FSH plays an important role in sexual development in children and fertility in adults.

In women who menstruate: FSH helps control the menstrual cycle by triggering the growth of eggs in the ovaries and preparing them for ovulation.
In men: FSH helps control the amount and health of sperm produced by the testicles (testes).
In children: FSH levels are normally low until puberty, at which point they rise to trigger physical changes. In girls, it stimulates the production of estrogen; in boys, it stimulates the production of testosterone.

FSH levels are controlled by a complex system involving the pituitary gland, the hypothalamus, and the reproductive glands (ovaries or testicles). Abnormal levels may indicate a problem with any of these parts.

What is it used for?

FSH testing is used to diagnose conditions that cause too much or too little FSH, depending on the patient's age and sex.

In women: Used to find the cause of infertility, check ovarian function, investigate irregular or stopped menstrual periods, and determine the onset of perimenopause or menopause.
In men: Used to investigate infertility, low sperm count, and conditions affecting the testicles.
In children and teens: Used to determine if a medical disorder is causing early or delayed puberty.
In both sexes: Used to help diagnose disorders of the pituitary gland or hypothalamus.

Why do I need an FSH levels test?

For women

Inability to get pregnant after 12 months of trying.
Irregular or stopped menstrual periods.
Symptoms of premature or early menopause.
Decreased interest in sex.

For men

Inability to help a partner conceive after 12 months of trying.
Decreased interest in sex.
Low sperm count.
Loss of muscle or body hair.

For children and teens

Early puberty: Signs of sexual development before age 8 in girls or age 9 in boys.
Delayed puberty: No signs of sexual development by age 13 in girls or age 14 in boys.

What happens during an FSH levels test?

A health care professional will take a blood sample from a vein in your arm using a small needle. The process typically takes less than five minutes.

What do the results mean?

Your provider will interpret results based on your sex, age, symptoms, and other hormone levels, such as luteinizing hormone (LH).

Higher levels of FSH: Often indicate a condition in the reproductive glands (such as primary ovarian insufficiency, PCOS, or testicular injury) or conditions like menopause. It may also indicate chromosomal disorders like Turner syndrome or Klinefelter syndrome.
Lower than normal levels of FSH: Often indicate a problem with the pituitary gland or hypothalamus. In women, this may also be linked to rapid weight loss, being underweight, or extreme exercise.

In children, high levels may indicate precocious puberty, while low or normal levels in teens with no signs of sexual development may indicate delayed puberty caused by conditions like hypogonadism or poor nutrition.