Follicle-stimulating hormone (FSH) is a reproductive hormone released by the pituitary gland. The FSH normal range varies depending on a woman's age and can even vary at different times of the month. It stimulates ovarian follicles in the ovary to grow the immature eggs contained inside and to produce estrogen. FSH blood levels are often used as one measure of fertility and whether a woman is approaching perimenopause or transitioning to menopause.
But FSH levels alone are not the sole indicator of where a woman is in her cycle or how close she is to perimenopause or menopause. FSH normal levels can be affected by other reproductive hormones such as estrogen, progesterone, testosterone, and luteinizing hormone (LH), so they are frequently tested together. Medications can also affect the normal FSH range.
FSH levels are measured from a blood sample. For infertility testing, the lab work is usually performed on the third day of the menstrual cycle. FSH level testing can also show pituitary or hypothalamic disorders and whether a woman is entering perimenopause or menopause. Women can also review the Menopause Rating Scale (MRS) can help her decide if she has additional low estrogen symptoms.
Home hormone tests, similar to pregnancy tests, may be used to check FSH normal range levels. However, they are not as accurate as a blood test.
FSH normal levels chart
10 - 15 years: 0.9-8.9 IU/L
15 - 18 years: 0.7-9.6 IU/L
Follicular: 2.9-14.6 IU/L
Mid-Cycle: 4.7-23.2 IU/L
Luteal: 1.4-8.9 IU/L
During puberty, FSH levels start to rise as the body matures and begins to respond to the reproductive hormone called gonadotropin-releasing hormone (GnRH). GnRH stimulates the release of FSH. The amount of FSH increases and falls each month when a woman starts to have regular menstrual periods.
There are four phases of the menstrual cycle:
- Follicular phase
- Ovulation (mid-cycle) phase
- Luteal phase
Menstruation is the shedding of the lining in the uterus lasting three to seven days and usually occurs every month.
The follicular phase begins on the first day of menstruation and ends with ovulation. During the years when women are fertile, FSH levels rise higher each month and stimulate several ovarian follicles to produce immature eggs. As estrogen levels increase, the hypothalamus secretes GnRH, stimulating more FSH and LH release from the pituitary. LH ultimately triggers ovulation, usually of a single egg.
The ovulatory or mid-cycle phase is where the egg is swept towards the fallopian tubes for fertilization and implantation into the uterus. It is the peak time of FSH secretion, so FSH levels will be at their highest.
The luteal phase lasts approximately two weeks after ovulation. FSH and LH levels fall, and estrogen levels decrease while progesterone levels rise. Both hormones are produced by the ovarian follicle to ready the uterus to accept the fertilized egg for implantation. Estrogen and progesterone continue to be produced to maintain the uterine lining. If pregnancy does not occur, the remains of the ovarian follicle whither, the uterine lining sheds during menstruation, and the cycle repeats the next month.
What low FSH levels might indicate
A condition that may affect these areas of the body.
- Are underweight or have recently lost weight
- Are not ovulating
- Are not producing necessary hormones due to a problem with the pituitary or hypothalamus
- Are pregnant
- Are on medications that may lower FSH levels
What high FSH levels might indicate
A condition that could affect fertility.
- Primary ovarian insufficiency (POI) can occur before age 40 where the ovaries no longer produce eggs.
- Polycystic ovary syndrome (PCOS) causes multiple follicles and cysts in the ovaries, and high levels of the male hormone testosterone affect menstruation and ovulation.
- Ovarian tumor that is benign or cancerous
- Turner syndrome is (a genetic disease), which also impairs fertility.
- Have a possible pituitary tumor
- Are in perimenopause or menopause
- Are on hormone therapy or other medications that elevate the FSH level
When do FSH levels indicate perimenopause?
The pituitary secretes FSH to stimulate ovarian follicle development and production of estrogen during a woman's most fertile years. But as she reaches perimenopause, there are fewer follicles left in her ovaries to mature. As the number of follicles decreases, so does the amount of estrogen.
FSH levels during perimenopause rise as the brain attempts to boost the level of estrogen production by putting out more FSH. Since the body's estrogen levels continue to decrease, the brain's feedback mechanism telling it to stop secreting more FSH, does not work. The brain (pituitary) continues to produce even more FSH instead, and FSH levels rise higher. During this erratic time of perimenopause, which can last months to several years, a woman may continue to have irregular menstrual periods and bursts of times where estrogen levels are high and low.
During perimenopause, FSH levels can rise above 30 mIU/mL. However, a single FSH level does not confirm a woman is in perimenopause or menopause. The FSH and estrogen levels do not fall steadily but can vary each day. If a woman experiences other symptoms such as hot flashes, irregular menstrual periods, or vaginal dryness, she is likely in perimenopause.
Additionally, FSH levels can also be affected if the woman takes hormone therapies such as birth control pills or other medications, so the FSH test may not be accurate.
Once a woman has not had a menstrual period for at least 12 consecutive months, her doctor will order lab work to see if it consistently shows elevated FSH levels along with changes in other reproductive hormones. In menopause, FSH levels may rise to 70-90 IU/L or higher. If her FSH levels are elevated and no other conditions are determined to be present, her doctor will likely determine that she has entered the period of menopause.
After menopause, a woman’s estrogen levels will naturally decline. A woman may decide to try supplements to raise her estrogen levels either orally or topically. Some women explore the use of herbs to improve their hormone balance before considering hormone replacement therapy.