Fertility blood test: Why does it need to be cycle days 2-5?

When you test your fertility with LEVY, you will always check your basic reproductive hormone levels (including FSH, LH, TSH, Prolactin, Estradiol, Progesterone, Anti Mullerian Hormone, Testosterone, DHEAS, SHBG, and Free Androgen Index). We also make a custom recommendation for other biomarkers to test based on your personal health background. It’s super important that you get your blood tested between the 2nd and 5th days of your cycle…and here’s why.

Certain reproductive hormones (FSH, LH, E2, and progesterone) fluctuate quite a bit during the course of the menstrual cycle. In order to get an accurate reading of these hormones, you need to measure them all at the beginning of the cycle (days 2-5), because this is when they are the most stable.

At the beginning of the cycle, FSH, LH, and E2 are low. FSH, or follicle-stimulating hormone, is responsible for growing and maturing the follicles in your ovaries that hold eggs. FSH levels rise to promote growth of the follicles and to prompt the secretion of estradiol (E2), which also plays an important role in ovulation. As you approach the middle of the cycle, LH surges, triggering release of the mature egg in ovulation. Following ovulation, the ovaries produce more progesterone to prepare the uterine lining for implantation.

Therefore, it’s crucial to test these hormones when they are at their baseline level (before they start to rise) to get a correct result. If you were to measure these hormones at a different time, say in the middle or towards the end of the cycle, you would get a completely different reading, and it wouldn’t be meaningful for your fertility. In order to get a full picture of your reproductive health, it’s necessary to look at your levels of these hormones along with other important biomarkers.

So while it may be a bit frustrating to have to wait until the beginning of your next cycle to get your blood drawn, we assure you it’s definitely worth the wait!

How do you know when it’s cycle days 2-5 and to get your fertility blood test?

You begin a new menstrual cycle on the first day of “real bleeding”. This means that it’s more than a few drops of blood coming out and you need to use a menstrual product to prevent blood from soaking through your underwear or clothes.

Even if your cycle is very irregular and the length varies quite a bit month to month, it’s still important to test at the beginning (between the 2nd to 5th day) to get a proper reading of your hormones.

The only exception here is if you have amenorrhea, or no period at all. Women with amenorrhea can usually get their blood drawn at any time, but sometimes may need to get an ultrasound first. In case the uterine lining is very thick, a doctor may need to induce menstrual bleeding before testing reproductive biomarkers. If you don’t have a period, check with the LEVY Care Team or ask your OB-GYN prior to having your blood drawn.

To learn more about our comprehensive fertility analysis, check out our article: What to expect when testing your fertility with LEVY.

Sources:

Ovarian Reserve. ReproductiveFacts.org from the American Society for Reproductive Medicine. Accessed 24 August 2022.

Fertility blood tests: Information for patients. Sheffield Teaching Hospital, NHS Foundation Trust.

FSH, E2 & Progesterone. Fertility Associates. Accessed 24 August 2022.

Day 3 FSH Fertility Testing of Ovarian Reserve – Follicle Stimulating Hormone Test. Advanced Fertility Center of Chicago. Accessed 24 August 2022. 

Hehenkamp WJK et al.: Anti-Müllerian Hormone Levels in the Spontaneous Menstrual Cycle Do Not Show Substantial Fluctuation. The Journal of Clinical Endocrinology & Metabolism, 2006;91(10):4057-4063.