A fertility hormone panel isn't one blood draw — it's several tests, and each one is only meaningful on the right day of your cycle. Draw the wrong hormone on the wrong day and the number can look abnormal when it isn't, or normal when it's actually telling you something. Here's what's timed, what isn't, and why.
The day-by-day answer
| Hormone | When to test | Why that day |
|---|---|---|
| FSH | Day 2 or 3 of your period | Read at its baseline, before the cycle's rising hormones change the picture — a level drawn later in the cycle isn't comparable to the reference ranges doctors use |
| Estradiol (E2) | Day 2 or 3, alongside FSH | Usually tested together with FSH as a pair — a high estradiol on day 2-3 can artificially suppress FSH, so the two are read as one baseline, not separately |
| LH | Day 2-3 for a baseline test; mid-cycle for surge detection | A day-2/3 blood LH is part of the same baseline panel as FSH. A different LH check — home ovulation strips, or a mid-cycle blood LH — is used to catch the surge that predicts ovulation, timed to when you expect to ovulate, not to day 2-3 |
| AMH | Any day of your cycle | Unlike the others, AMH doesn't fluctuate meaningfully with the cycle, so there's no "right day" to plan around — this is often the easiest test to fit into a busy schedule |
| Progesterone | About a week before your expected period (roughly day 21 in a 28-day cycle) | Progesterone only rises after ovulation, so testing it in the second half of the cycle is what confirms ovulation actually happened — testing early in the cycle would show nothing |
| Prolactin | Not cycle-day dependent, but draw it fasting, on a calm morning | Prolactin can rise transiently from stress, food, or even the blood draw itself, so timing relative to your cycle matters less than timing relative to your morning — a calm, fasting draw avoids a falsely high reading |
Why this matters more than it seems
Get the day wrong and one of two things happens: a genuinely abnormal result gets missed because it was diluted by the wrong cycle phase, or a genuinely normal result looks abnormal because it's being read against the wrong reference range — either way, you and your doctor end up making decisions on a number that doesn't mean what it appears to mean. This is also why a fertility hormone panel is rarely drawn all in one visit unless your doctor has specifically planned the timing around it.
If your periods are irregular enough that "day 2-3" is hard to pin down, tell your doctor rather than guessing — they can plan around it, or lean more on the tests (like AMH) that don't depend on cycle timing at all.
Frequently asked
Can I get all these tests done on the same day for convenience?
Not accurately. FSH, estradiol, and the baseline LH can be drawn together on day 2-3, and prolactin can usually be added to that same visit if it's a calm, fasting draw — but progesterone specifically needs the second half of the cycle to mean anything, so it can't be combined with the day 2-3 panel in one sitting.
What if I don't know exactly which day of my cycle I'm on?
Count from the first day of full flow as day 1 — spotting before that doesn't count. If your cycles are too irregular to predict reliably, say so when booking the test; your doctor may use a different approach (like tracking with ultrasound) rather than a fixed calendar day.
Does a mistimed test mean I have to repeat it?
Often, yes, if the timing was meaningfully off — a day-10 "FSH" or a day-3 "progesterone" usually can't be interpreted against standard ranges and gets repeated at the correct time rather than acted on.
Is AMH really not affected by cycle day at all?
Correct — it's one of the few fertility hormones where timing genuinely doesn't matter, which is why it's often the first test suggested when cycle tracking itself is difficult.