Fertility blood tests: which hormones are checked and when

You're trying to conceive — or planning to soon — and you've heard about "fertility blood tests." But which hormones get checked, why do some need to be drawn on day 21 and others on day 2 or 3, and what do the results actually tell you?

This guide explains the standard fertility blood panel in Australia, the timing rules that matter, and how to get the process started.

Why Fertility Blood Tests Are Done

Fertility blood tests measure the hormones that orchestrate your menstrual cycle and ovarian function. They're typically ordered to:

• Investigate why conception hasn't happened after 12 months of trying (or 6 months if you're over 35)
• Assess ovarian reserve — an estimate of how many eggs you likely have remaining
• Check for conditions like polycystic ovary syndrome (PCOS) or thyroid problems that affect fertility
• Confirm ovulation is actually occurring
• Establish a baseline before fertility treatment such as ovulation induction or IVF

Men get tested too — a semen analysis is usually the first male fertility test, often alongside hormone tests (testosterone, FSH, LH). Both partners are assessed together; fertility is a two-person picture.

The Key Fertility Hormones and What They Tell You

AMH (Anti-Müllerian Hormone)

• What it shows: a measure of your ovarian reserve — the approximate number of eggs remaining. Higher levels generally suggest a larger reserve; lower levels a reduced one
• When it's taken: any day of the cycle — one of the few fertility hormones that doesn't fluctuate much with your cycle. It can even be measured while you're on the pill, though results are interpreted with care
• What it doesn't show: AMH reflects quantity, not quality of eggs — and it doesn't predict your chance of conceiving naturally on its own. A low AMH doesn't mean pregnancy is impossible; it helps plan testing and treatment timing

FSH (Follicle-Stimulating Hormone)

• What it shows: the hormone from your brain's pituitary gland that recruits follicles each cycle. Persistently high FSH can indicate the ovaries are working harder in response to a lower reserve
• When it's taken: day 2–5 of your cycle (day 1 = the first day of full menstrual flow)

LH (Luteinising Hormone)

• What it shows: triggers ovulation mid-cycle. A very high LH relative to FSH is common in PCOS
• When it's taken: day 2–5 of your cycle, sometimes repeated mid-cycle

Oestradiol (E2)

• What it shows: the main oestrogen produced by growing follicles. Read together with FSH on a day 2–5 test — a high baseline oestradiol can mask or alter what FSH appears to say
• When it's taken: day 2–5 of your cycle

Progesterone

• What it shows: whether ovulation has occurred. After ovulation, the corpus luteum produces progesterone, which rises significantly
• When it's taken: about 7 days before your expected period — traditionally called "day 21," but only accurate for a 28-day cycle. If your cycle runs 32 days, it's around day 25. This timing error is one of the most common reasons for confusing results

Other Tests Commonly Added

• Thyroid hormones (TSH ± free T4): both overactive and underactive thyroid affect fertility and pregnancy
• Prolactin: elevated levels can suppress ovulation
• Androgens (testosterone, DHEAS): checked when PCOS is suspected
• Rubella immunity, blood group, and other preconception screen: often bundled in early pregnancy or pre-conception workups

The Cycle-Timing Cheat Sheet

Getting the day wrong matters: a progesterone taken on day 21 of a 35-day cycle may look "low" simply because you hadn't ovulated yet — or had already passed peak. Always test against your cycle length, not the textbook average.

What Happens at the Pathology Centre

• 1. Book or walk in to a pathology collection centre — most don't need appointments for blood tests, but some fertility-specific collections do
• 2. Timing is your responsibility — the lab doesn't know your cycle day unless you tell them; ring ahead if a specific-day draw is required
• 3. A standard blood draw takes a few minutes — one or two small tubes
• 4. Results go to your referring doctor, typically within 1–3 days for routine hormones

You can get a pathology referral online through NewTeleDoc Medical from $25: an AHPRA-registered GP assesses your situation by telehealth and sends a referral to a collection centre near you, digitally. See our guide to getting a blood test referral online.

How to Read Your Results — With a GP, Not a Lab Portal

Hormone results are not pass/fail. They're interpreted against your age, cycle day, medications and clinical history. Common patterns:

• High FSH with low AMH → suggests diminished ovarian reserve; may prompt earlier referral to a fertility specialist
• High LH:FSH ratio with raised androgens → consistent with PCOS
• Low mid-luteal progesterone → may mean ovulation didn't occur that cycle (or timing was off)
• Abnormal TSH or prolactin → treatable conditions that often restore regular ovulation once managed

Your GP can explain your numbers, repeat any borderline tests, and refer you to a fertility specialist when appropriate — referrals are available online from $25.

When to See a Fertility Specialist

Most GPs recommend specialist referral after:

• 12 months of unprotected intercourse without conception if you're under 35
• 6 months if you're 35 or older
• Sooner if you have known risk factors — irregular cycles, PCOS, endometriosis, previous ectopic pregnancy, or a partner with a known issue