I'm writing this article because of a conversation I wasn't prepared for.
My girlfriend was diagnosed with PCOS a few years ago — I've written about that here. The diagnosis was a process: years of symptoms, eventual blood work and ultrasound, a name for something she'd been fighting without understanding. We'd dealt with the metabolic side, the hormonal side, the emotional side. I thought we'd crossed the hardest terrain.
Then we started talking about having kids.
And suddenly PCOS wasn't just a condition she managed. It was a fertility question. That question (can I have children?) carried a weight that nothing else in the diagnostic process had. Not the irregular periods. Not the weight struggle. Not the insulin resistance. Fertility was the one that sat in her chest and wouldn't move.
She wanted to test. Not because we were trying to conceive right then, but because she needed to know where she stood. She wanted data. Something concrete. Something other than the anxiety of not knowing.
So she ordered an AMH test, along with FSH and a hormonal panel. And I sat next to her when she opened the results.
This article came out of that experience. It covers the blood tests used in fertility assessment, what each one measures, what the results can and can't tell you, and the critical distinction between ovarian reserve and actual fertility. A distinction that a lot of the marketing around these tests doesn't make clear.
I'm a man writing about women's fertility. I'm aware of the irony. But I watched someone I love navigate this process, and I think the information gap is real. According to the Australian Institute of Health and Welfare, approximately one in six Australian couples experience a delay of more than a year in achieving a planned pregnancy. One in eighteen babies born in Australia is now conceived through assisted reproductive technology (ANZARD data). These aren't fringe statistics. This is a mainstream health concern that deserves clear, honest information.
A note before we get into it
General information only. I'm not a doctor or a fertility specialist. Fertility is profoundly personal and clinically complex. Blood tests are one component of a broader fertility assessment that may include physical examination, imaging, and partner evaluation.
If you're actively trying to conceive and concerned about fertility, or if you're investigating why conception hasn't occurred, please work with your GP or a fertility specialist. This article is about understanding the tests, not replacing clinical advice.
What fertility blood tests can and can't tell you
Before we get into the individual tests, I want to set a frame that I think is missing from a lot of the content out there.
Blood tests can:
Measure hormone levels that reflect ovarian function and reproductive health. Indicate ovarian reserve (the quantity of remaining eggs). Identify hormonal imbalances that may affect ovulation. Detect thyroid dysfunction or other conditions that impact fertility. Flag metabolic issues like insulin resistance and blood sugar dysregulation relevant to conception and pregnancy. Help guide treatment decisions in assisted reproduction.
Blood tests cannot:
Tell you whether you will or won't get pregnant. Assess egg quality (only quantity). Predict the timing of natural conception. Replace a comprehensive fertility assessment, which includes partner evaluation, imaging, and clinical history. Account for the many non-hormonal factors that affect fertility: tubal patency, uterine anatomy, sperm quality, timing, and age itself.
This distinction matters because the marketing around some fertility tests, particularly AMH, can imply a level of predictive power that the evidence doesn't support. I'll get into this more in the AMH section. For now: blood tests give you important data points, not a verdict.
The key tests
AMH (Anti-Müllerian Hormone)
What it measures
AMH is produced by the small follicles in your ovaries and reflects your ovarian reserve — the quantity of eggs remaining.
Why it's the most requested fertility test
AMH has become the go-to marker for ovarian reserve because it's convenient (can be tested any day of the cycle, not affected by hormonal contraception in most cases), relatively stable, and provides a snapshot of where your egg reserve sits relative to other women your age.
The critical caveat
AMH doesn't measure egg quality. A woman with a low AMH and excellent egg quality may conceive naturally. A woman with a high AMH and poor egg quality may not. AMH tells you about the size of the remaining pool, not the viability of what's in it.
I'll cover AMH in more detail below. It deserves its own section because of how widely it's discussed and how commonly it's misunderstood.
Test it with Bloody Good:
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FSH (Follicle-Stimulating Hormone)
What it measures
FSH is the pituitary hormone that stimulates follicle growth in the ovaries. It's measured in the early follicular phase (days 2–5 of the menstrual cycle).
How it reflects ovarian reserve
FSH levels reflect how hard the pituitary is working to stimulate follicle development. In women with good ovarian reserve, FSH stays relatively low because the ovaries respond efficiently. When ovarian reserve declines, the pituitary ramps up FSH production to try to push the ovaries harder. Elevated early-cycle FSH is a signal of diminished ovarian reserve.
The limitation
FSH can vary significantly between cycles. A single elevated reading should be interpreted with caution and ideally confirmed. It's also less sensitive than AMH for detecting early decline. By the time FSH rises consistently, ovarian reserve may already be significantly diminished.
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LH (Luteinising Hormone)
What it measures
LH is the pituitary hormone that triggers ovulation — the release of a mature egg from the follicle.
The fertility connection
The LH surge in the middle of the cycle is what prompts ovulation. Baseline LH (measured in the early follicular phase) provides context about the hormonal environment. In PCOS, LH is often elevated relative to FSH, reflecting disrupted ovulatory signalling.
LH is most useful as part of a broader panel rather than in isolation. It helps characterise the type of ovulatory dysfunction, if present.
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Oestradiol (E2)
What it measures
The primary form of oestrogen, produced by developing follicles in the ovaries.
Why it's tested alongside FSH
Early-cycle oestradiol (days 2–5) is measured alongside FSH. If oestradiol is elevated at this stage, it may be artificially suppressing FSH, making FSH look normal when it's actually being masked. This is a technical nuance, but it's the reason clinicians test both together.
Oestradiol also plays a role in preparing the uterine lining for implantation and in supporting follicular development.
Test it with Bloody Good:
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Progesterone
What it measures
Progesterone rises after ovulation and is essential for preparing the uterine lining for embryo implantation and maintaining early pregnancy.
Confirming ovulation
A mid-luteal phase progesterone test (roughly day 21 of a 28-day cycle, adjusted for cycle length) confirms whether ovulation has occurred. If progesterone is low at this point, it suggests anovulation: the follicle didn't release an egg, or the corpus luteum isn't producing adequate progesterone.
Timing is everything
This test must be timed to the luteal phase. A "day 21" progesterone in a woman with a 35-day cycle will be too early and may produce a falsely low result. Work with your clinician to time it correctly based on your individual cycle.
Test it with Bloody Good:
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Thyroid Function (TSH)
What it measures
Thyroid-stimulating hormone, the primary screening marker for thyroid dysfunction.
The fertility impact
Thyroid dysfunction, both hypothyroidism and hyperthyroidism, can affect ovulation, menstrual regularity, implantation, and early pregnancy outcomes. Even subclinical hypothyroidism (mildly elevated TSH) has been associated with reduced fertility and increased miscarriage risk in some studies.
The 2023 PCOS guideline and pre-conception care recommendations both include TSH screening. If you're planning pregnancy, thyroid function should be checked.
For more detail on thyroid testing, see our thyroid function test guide.
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Prolactin
What it measures
A hormone produced by the pituitary gland, primarily known for its role in milk production.
When it disrupts ovulation
Elevated prolactin (hyperprolactinaemia) can suppress GnRH, which in turn suppresses FSH and LH, disrupting ovulation. It's one of the conditions that needs to be excluded when investigating irregular periods or anovulation.
Prolactin can be transiently elevated by stress, certain medications, nipple stimulation, and even the stress of the blood draw itself. If your result is mildly elevated, a repeat test is usually recommended before drawing conclusions.
Test it with Bloody Good:
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The metabolic and nutritional tests that matter for fertility
Fertility isn't just about reproductive hormones. Your metabolic and nutritional health form the foundation.
Iron studies (including ferritin): Iron deficiency is common in women of reproductive age and can affect energy, ovulatory function, and pregnancy outcomes. If you're planning pregnancy, adequate iron stores before conception are significantly easier to maintain than trying to replenish during pregnancy when demand doubles. See our iron and ferritin guide.
Vitamin D: Low vitamin D has been associated with reduced fertility outcomes in some studies, though the evidence is still evolving. It's commonly low in Australian women (one in four are deficient, according to the ABS 2011–12 Australian Health Survey) and easily corrected. See our vitamin D guide.
HbA1c and fasting glucose: Blood sugar regulation matters, particularly for women with PCOS or insulin resistance. Uncontrolled blood sugar increases the risk of gestational diabetes and adverse pregnancy outcomes. Pre-conception metabolic screening is recommended. See our HbA1c guide.
Vitamin B12 and folate: Both are essential for red blood cell production and neural tube development. Folate supplementation before and during early pregnancy is one of the most well-established preventive measures in obstetrics.
Thyroid function: Already covered above. Worth emphasising: target TSH ranges during pregnancy are tighter than for the general population, and thyroid dysfunction can emerge or worsen during pregnancy.
AMH: the test everyone asks about
AMH deserves its own section because it's the test with the biggest gap between marketing and evidence.
What AMH tells you: The size of your remaining follicular pool. AMH is produced by the small antral and pre-antral follicles in your ovaries. A higher AMH generally reflects a larger pool of remaining eggs. A lower AMH reflects a smaller pool.
What AMH is genuinely useful for:
Predicting response to IVF stimulation (how many eggs are likely to be retrieved). Contextualising ovarian reserve relative to your age. Flagging very low reserve that may warrant earlier investigation or action. Supporting PCOS diagnosis (AMH is often elevated in PCOS, though the 2023 guideline recommends against using it as a standalone diagnostic tool).
What AMH doesn't do, despite what some marketing implies:
It doesn't predict whether you'll conceive naturally. It doesn't assess egg quality. It doesn't tell you when you'll reach menopause (though very low levels may warrant investigation). It doesn't have reliable predictive value for individual women. Population-level associations don't translate cleanly to individual outcomes.
A landmark 2017 study (Steiner et al., published in JAMA) followed women aged 30–44 who were trying to conceive and found that women with low AMH levels did not have a meaningfully lower probability of conceiving naturally compared to women with normal levels. The study concluded that AMH was not associated with reduced fertility in women without a known history of infertility.
This matters. A low AMH result in a woman who is trying to conceive naturally shouldn't be interpreted as "you can't get pregnant." It means her egg reserve is lower than average, which has implications for IVF response and possibly for the timeline of her remaining fertility. But it's not a fertility prognosis.
The emotional weight of an AMH number can be enormous. I watched my girlfriend process hers. It wasn't low. It was actually on the higher side, consistent with her PCOS. But even so, the moment of opening that result and trying to map it onto "will I be able to have children" was visceral. I can only imagine what it's like for women who get a low number without the context to understand what it does and doesn't mean.
If you test your AMH, please interpret it with your clinician. Not with Google. Not with a fertility clinic's marketing page. With someone who can place the number in the context of your age, your cycle, your overall health, and your actual fertility goals.
When to test — and when not to panic
Testing makes sense if:
You've been trying to conceive for 12 months (or 6 months if you're over 35) without success. You're planning pregnancy in the next 1–2 years and want a baseline understanding of your reproductive health. You have irregular periods, signs of hormonal imbalance, or a diagnosed condition like PCOS. You have a family history of early menopause or premature ovarian insufficiency. You're considering egg freezing and want to understand your ovarian reserve. You're about to start fertility treatment and your specialist needs baseline data.
Testing does not mean:
That you're broken. That you're running out of time. That you need IVF. That a number on a page determines your future as a parent.
Fertility is not a single test result. It's the intersection of age, egg quality, egg quantity, hormonal balance, uterine health, tubal patency, partner factors, timing, and a fair amount of chance. Blood tests illuminate part of that picture. An important part. But only a part.
How to get useful results
Timing matters for most fertility hormones. FSH, LH, and oestradiol should be tested in the early follicular phase — days 2–5 of your menstrual cycle. Progesterone is tested mid-luteal phase (approximately day 21 of a 28-day cycle, adjusted for your actual cycle length).
AMH can be tested any day. It's not significantly affected by your cycle phase, which makes it the most convenient of the fertility markers.
Morning testing is preferred for most hormones, though it's less critical than for cortisol or testosterone.
Stop biotin supplements 48–72 hours before testing. Biotin can interfere with some immunoassays.
Tell your clinician about hormonal contraception. The oral contraceptive pill can suppress FSH and LH and may affect some markers. AMH is generally considered reliable regardless of OCP use, though some newer research suggests a modest effect. Discuss with your clinician.
Don't test in isolation. A single set of fertility bloods without clinical context (your age, cycle history, symptoms, partner factors) is data without a framework. Get the blood work done, then discuss with your GP or specialist.
Understanding your results
AMH (age-dependent, ranges vary by lab):
| Result | What it suggests |
|---|---|
| High | May suggest PCOS (in the right clinical context) or good ovarian reserve |
| Normal for age | Reassuring regarding egg quantity |
| Low for age | Suggests diminished ovarian reserve. Worth discussing with a specialist, particularly if conception is a goal. |
| Very low (<5 pmol/L) | Significantly reduced reserve. Earlier action may be advisable. |
FSH (early follicular, days 2–5):
| Result | What it suggests |
|---|---|
| Below 10 IU/L | Generally reassuring |
| 10–15 IU/L | May suggest early decline in ovarian reserve |
| Above 15 IU/L | Suggests diminished ovarian reserve. Correlate with AMH and clinical picture. |
LH (early follicular):
Elevated relative to FSH suggests a PCOS pattern. Normal levels are part of the baseline picture.
Oestradiol (early follicular):
Below 200 pmol/L is expected at this cycle stage. Elevated oestradiol may be masking an elevated FSH. Repeat testing is recommended.
Progesterone (mid-luteal, ~day 21):
Above 25 nmol/L indicates ovulation has likely occurred. Below 15 nmol/L suggests anovulation or poor luteal function.
TSH:
Pre-conception target: ideally below 2.5 mU/L (tighter than the general population range).
Tests to consider through Bloody Good
Core fertility hormones:
| Test | When to test |
|---|---|
| AMH Blood Test | Any day of cycle |
| FSH Blood Test | Early follicular phase (days 2–5) |
| LH Blood Test | Early follicular phase |
| Oestradiol Blood Test | Early follicular phase |
| Progesterone Blood Test | Mid-luteal phase (~day 21) |
Hormonal context:
| Test | Purpose |
|---|---|
| Prolactin Blood Test | Rule out hyperprolactinaemia |
| Thyroid Function Test (TFT) | Thyroid screening |
| Testosterone Free/Total + SHBG | If PCOS is suspected |
Pre-conception health:
| Test | Why it matters |
|---|---|
| Iron Studies (Including Ferritin) | Build stores before pregnancy |
| Vitamin D (25-OH) | Commonly deficient, easy to correct |
| Vitamin B12 | Essential for neural tube development |
| Folate | Essential for neural tube development |
| HbA1c | Metabolic screening |
| Full Blood Count (FBC) | Baseline blood health |
If you want broad coverage:
The Bloody Good Test covers 100 biomarkers including many of the above. For women establishing a pre-conception baseline, combining the comprehensive panel with specific fertility hormones (AMH, FSH, progesterone) gives the most complete picture.
What to do after testing
If results are reassuring: That's good news. Keep it in perspective. Reassuring results don't guarantee conception, but they remove some of the anxiety about whether something is obviously wrong. Continue with pre-conception health basics: folate supplementation, iron optimisation, vitamin D adequacy, thyroid within target range.
If results suggest diminished ovarian reserve: Don't panic, but do act. A conversation with a fertility specialist sooner rather than later is advisable. Diminished reserve doesn't mean you can't conceive, but it may mean the timeline is shorter than average, and options like egg freezing may be worth discussing.
If results suggest a hormonal imbalance: Many of these are treatable. Thyroid dysfunction, hyperprolactinaemia, and PCOS-related anovulation all have established management pathways. A diagnosis gives your clinician something to work with.
If results are mixed or unclear: Fertility is complex. One set of bloods rarely gives you the whole answer. Your GP or specialist may recommend repeat testing, additional investigations (ultrasound, semen analysis for your partner), or referral to a fertility clinic for a comprehensive workup.
Regardless of results: Fertility is not fully captured by numbers on a page. Age remains the single strongest predictor of natural fertility. Blood tests add important information, but they're one part of a much bigger picture. The most useful thing you can do with your results is take them to someone qualified to interpret them in the context of your whole story.
Explore more biomarkers
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General information only. This article is not medical advice and is not a substitute for care from a qualified health professional. If you have concerning symptoms or urgent health issues, seek medical attention promptly.