Understanding FSH levels: how FSH levels are connected to age and fertility

Medically reviewed by Rosanna Sutherby, PharmD on March 15, 2021. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.


Did you know the follicle-stimulating hormone (FSH) has an effect on everything from fertility to menopause? Knowing what normal FSH levels are and when to check your own FSH levels could help you better understand your own reproductive health. Here, we break down FSH levels by age and how FSH levels relate to fertility, so read on.

What is follicle-stimulating hormone (FSH)?

Hormones are the body’s “chemical messengers” that help regulate many different processes and functions in the body. Follicle-stimulating hormone, or FSH, is a hormone released by the pituitary gland (located at the base of the brain) that plays a key role in the menstrual cycle.

During the first half of the menstrual cycle, increased levels of FSH work in concert with luteinizing hormone (LH) to tell the ovaries to make more estradiol (estrogen), while also recruiting and stimulating an egg in the ovary to mature for ovulation.

FSH is typically measured on days 3-4 of a normal cycle because this gives a good baseline level for FSH before it begins rising rapidly during the ovulatory phase of the menstrual cycle.

What are normal FSH levels by age?

Like most other hormones, normal FSH levels are typically determined by comparing your test result to a reference range.

Generally, normal FSH levels by age are considered to be the following (with measurements based on day 3 of a normal cycle):

  • Age 33 or under: less than 7.0 mlU/mL (milli-international units per milliliter)
  • Age 33-37: less than 7.9 mIU/mL
  • Age 38-40: less than 8.4 mIU/mL
  • Age 41 and over: less than 8.5 mIU/mL

However, it’s important to keep in mind that reference ranges for FSH levels differ depending on the laboratory that’s doing the testing. This is a regular aspect of the lab testing process, so when determining if your FSH levels are normal for your age, it’s best to compare your level with the reference range set by the laboratory that did the FSH testing for you.


When you take our at-home Ovarian Reserve Test or Women's Fertility Test to check your FSH level, you receive easy-to-understand digital results that tell you how your FSH level compares to the reference range.


How are FSH levels connected to fertility?

As women age (typically beginning in their 30s), their levels of FSH increase in response to a natural decrease in egg quantity, also called “ovarian reserve.” As the total number of eggs gets smaller, it becomes harder for the ovaries to produce a mature egg for ovulation—so the pituitary gland produces more FSH to give them extra stimulation. Thus, FSH levels can act as an indirect indicator of how many eggs a woman might have left, and a diminished ovarian reserve can contribute to difficulty getting pregnant and overall infertility.

In this way, FSH testing may help you better understand your ovarian reserve and provide information that can be helpful and relevant for your fertility. Of course, it’s a good idea to share your results with your healthcare provider and/or your OB/GYN. They will be able to assess your results in combination with a physical exam, your medical history, and other factors.

Want to better understand if your ovarian reserve may be normal for your age? Shop the Everlywell at-home Ovarian Reserve Test and get digital results days after you mail your sample to the lab for testing.

References

1. FSH Levels by Age - Follicle Stimulating Hormone Levels with Chart. Center for Human Reproduction. URL. Accessed March 15, 2021.

2. Rasool S, Shah D. Fertility with early reduction of ovarian reserve: the last straw that breaks the Camel's back. Fertil Res Pract. 2017;3:15. Published 2017 Oct 11. doi:10.1186/s40738-017-0041-1

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