What Is The FSH Levels (Day 3 FSH) Test:
As part of a basic fertility work-up, your doctor will likely order blood work to check your FSH levels, specifically on day 3 of your menstrual cycle. Sometimes called the Day 3 FSH test, it is a simple blood test meant to measure the amount of FSH in your bloodstream.
FSH, otherwise known as follicle stimulating hormone, is a hormone that tells oocytes, or premature eggs, to begin growing. Each oocyte is contained within a follicle, or little fluid sac. The growth and development of the oocytes is the first part of the process that will, ideally, lead to ovulation.
You can read more about ovulation here.
When Are FSH Levels Checked:
The test is usually given on day 3 of your menstrual cycle, though most doctors are OK with the test being done on any day between days 2 to 4 of your cycle. (The first day of your cycle is the day your period begins.)
FSH levels may also be checked at another time during the menstrual cycle, but this is uncommon.
Why Are FSH Levels Important:
High levels of FSH may indicate poor ovarian reserves. In layman’s terms, it means that the quantity and quality of your eggs is low. While high FSH levels do indicate that you may have more difficulty getting pregnant, they don’t mean that you cannot get pregnant. Your FSH levels are just one factor to be taken into consideration.
How Is An FSH Levels Blood Test Done:
The blood test is like any other blood test. Your doctor will tell you when to have the test done, most likely on day 3 of your menstrual cycle. For the test, a nurse will draw blood from a vein in your arm. You may feel a small pinch, but the test is essentially pain-free and simple.
What Are Considered To Be Normal FSH Levels:
The normal range for FSH levels will vary between labs. You need to speak to your doctor for an accurate interpretation. Also, comparison with your LH levels and estrogen levels (specifically estradiol, or E2) is required, to get the entire picture.
With that said, a study on day 3 FSH levels and IVF outcomes showed that women with day 3 FSH levels less than 15 mIU/ml had a better chance of pregnancy achievement per IVF attempt, when compared to women with FSH levels between 15 mIU/ml and 24.9 mIU/ml. For women with day 3 FSH levels over 25 mIU/ml, pregnancy rates per attempt were even lower.
How Are FSH Levels Interpreted:
Generally, high FSH and/or estradiol may indicate poor ovarian reserves.
If both LH and FSH are abnormally low, this may indicate a problem with the functioning of the pituitary or hypothalamus, two parts of the brain which play an important role in ovulation.
Sources:
Infertility: An Overview. American Society of Reproductive Medicine. Accessed August 20, 2008. http://www.asrm.org/Patients/patientbooklets/infertility_overview.pdf
FSH. Lab Tests Online. American Association for Clinical Chemistry. Accessed August 20, 2008. http://labtestsonline.org/understanding/analytes/fsh/test.html
LH. Lab Tests Online. American Association for Clinical Chemistry. Accessed August 20, 2008. http://labtestsonline.org/understanding/analytes/lh/glance.html
Prediction of Fertility Potential (Ovarian Reserve) in Women. Patient Fact Sheet. American Society of Reproductive Medicine. Accessed August 20, 2008. http://www.asrm.org/Patients/FactSheets/Older_Female-Fact.pdf
Scott RT, Toner JP, Muasher SJ, Oehninger S, Robinson S, Rosenwaks Z. Follicle stimulating hormone levels on cycle day 3 are predictive of in vitro fertilization outcome. Fertility and Sterility. 1989; 51:651-4.
