Lab Results · 5 min read · Due Team
How to Read Your Day 3 Labs: FSH, LH, and Estradiol Explained
Day 3 bloodwork is a standard first step in a fertility workup. Here's what each number measures, what the ranges mean, and how to read them together.
Day 3 labs — drawn on the third day of your period — give your provider a snapshot of your baseline hormonal environment. Three values matter most: FSH, LH, and estradiol (E2).
FSH (Follicle-Stimulating Hormone)
- Normal day 3 FSH: Generally below 10 mIU/mL
- Elevated FSH (above 10): Suggests reduced ovarian reserve
- Very high FSH (above 20): Associated with significantly diminished reserve
FSH can vary cycle to cycle. The highest value you've recorded is typically the most clinically meaningful.
LH (Luteinizing Hormone)
On day 3, LH should be low and roughly similar to FSH. An elevated LH relative to FSH — particularly an LH:FSH ratio above 2:1 or 3:1 — can suggest PCOS.
Estradiol (E2)
Day 3 estradiol should be below 80 pg/mL. An elevated estradiol on day 3 can artificially suppress FSH, making FSH look normal even when it isn't. This is why estradiol is always checked alongside FSH.
The bottom line
Day 3 FSH, LH, and estradiol give a baseline hormonal snapshot. Always check estradiol alongside FSH — it provides critical context for interpreting the result.
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