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What is FSH & How Does it Affect My Fertility?

Written by:, PhD, Founder and Inventor of the Proov test — the first and only FDA-cleared test to confirm successful ovulation at home.

It can be hard to keep track of all the hormones people are talking about – FSH, AMH, LH, oh my! Fortunately at Proov, we’ve made it our mission to help you understand your hormones and your fertility, so we’re here to break it all down for you. 

If you’re looking for a broad overview of the main menstrual cycle hormones, check out this article. If you’re ready to learn all about FSH (follicle stimulating hormone), your future fertility, and why it matters, read on! 

What is FSH (Follicle Stimulating Hormone)?

Follicle-stimulating hormone (FSH) is the first hormone that’s active at the beginning of a new menstrual cycle (right after you get your period). Follicle-stimulating hormone is a protein that acts as a chemical messenger, coming from your pituitary gland in the brain and traveling down to your ovaries. 

FSH does exactly what its name says – it stimulates several follicles (small sacs containing immature eggs) in the ovaries to begin growing. It also causes an increase in estrogen production. As one follicle becomes dominant, it will make high levels of estrogen and suppress more FSH from being released. What follows is ovulation, but that’s a story for another day! 

Through the rest of the cycle, estrogen and progesterone will prevent FSH from rising again and stimulating more follicles. When hormone levels drop during menstruation, it allows FSH to start the entire process over again! 

As you age, it becomes more difficult for FSH to successfully stimulate follicles, so FSH levels will have to rise (basically, the pituitary gland has to work harder and send more FSH) to achieve the same results. Once your FSH levels reach 25 mIU/mL and you haven’t had a period in a year, you are considered to be in menopause. 

What is a follicle stimulating hormone levels test? 

An FSH test is in some ways exactly what it sounds like! It’s just a test, either with blood or urine, performed on specific days of your menstrual cycle and providing you with your FSH levels. You can go into a clinic for a blood test, or use an at-home kit, but either way it will provide FSH levels at a single time point.  

For more convenient urine testing, Proov Reserve FSH tests work similarly to a pregnancy test or LH test. These FSH tests are sticks that you dip into a urine sample, and along with the help of the Proov Insight App, detect your FSH levels on days 5, 7, and 9 of your cycle, with the first day of your period being cycle day 1.

While an FSH test is testing the levels of the hormone directly, it’s indirectly doing something much more important, and that’s testing your ovarian reserve. Ovarian reserve is another way of saying how many eggs you have left, and decreased ovarian reserve can indicate that you might have challenges with fertility treatments or, if your FSH levels are too high, you may be entering menopause soon. 

Remember that FSH is backwards compared to most other reproductive hormones–that is, instead of wanting FSH to be pretty high to be in the optimal range, it’s better for FSH levels to be relatively low. Higher FSH levels mean your reproductive system has to work harder to stimulate follicles and ultimately ovulate successfully. 

Why do I need one? 

Why would you want to test your FSH in the first place? Mainly, FSH tests can be useful for two reasons: either you’re concerned about your future fertility and want to test your ovarian reserve, or if you’re considering fertility treatments such as ovulation induction or IVF (both of which have statistically reduced outcomes for women with high FSH levels).

While FSH levels don’t actually have any bearing on your ability to conceive naturally right now (unless you’re very close to menopause), they can provide useful information about your future fertility, especially if you’re at risk for primary ovarian insufficiency (this means that your ovarian reserve is lower than would be expected based on your age). Primary ovarian insufficiency might make it more difficult for you to conceive later on. 

You might want to test if you’re planning on having children later, especially after age 35, or if your mother or another female relative was diagnosed with primary ovarian insufficiency or early menopause. 

FSH & Fertility 

FSH is more important for your current fertility than your future fertility. While FSH levels might be high right now, that doesn’t mean that you aren’t ovulating successfully or able to get pregnant. To predict and confirm ovulation, and find your fertile window, you’ll need to test other hormones, specifically estrogen, LH, and progesterone. 

Studies have shown that women with high FSH don’t have a reduced chance of conceiving naturally. However, if you’re considering fertility treatments like IVF, high FSH may be a barrier as it reduces your chances of getting enough eggs required for the IVF process. If that’s your scenario, talk to your fertility specialist about whether or not they have a cutoff FSH level. 

If your FSH levels are high for your age but you’re currently trying to conceive and experiencing challenges, it’s helpful to look elsewhere first such as confirming successful ovulation and making sure you’re timing intercourse correctly. Keep in mind that decreased ovarian reserve may make it more challenging to get pregnant as you age. 

How to Interpret Test Results

Finally, now you know why FSH tests matter, maybe you’re considering taking one, but what do you do when you get the results? With Proov Reserve, the free Proov Insight App will read and interpret your test for you. Here’s an overview of what your FSH levels might mean! 

  • 0-4 mIU/mL: Normal FSH levels in females past puberty should be above 4 to trigger follicular development. FSH levels lower than this may indicate a problem and you should talk to your physician.
  • 5-10 mIU/mL: This is the optimal range for those in their 20s and indicates a high ovarian reserve.
  • 11-15 mIU/mL: FSH is slightly elevated, indicating slightly decreased ovarian reserve. This is typical if you’re in your 30s. 
  • 16-24 mIU/mL: This is elevated FSH, typical in late 30s and early 40s. FSH levels here are commonly accompanied by perimenopause symptoms, and may be too high for fertility treatments to be successful. 
25+ mIU/mL: FSH over 25 is one of the indicators of menopause (along with no period for a year) and is perfectly normal if you’re over 45. If you’re significantly younger, this may be a sign of primary ovarian insufficiency and you should consult a physician.
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