Ovarian Reserve Testing: AMH, AFC and FSH Compared
An AMH result arrives as a single number with a reference range beside it, and almost no explanation. Within an hour most women have searched it, found a chart suggesting their ovaries belong to someone a decade older, and concluded something that is probably not true.
Ovarian reserve testing is a standard part of a fertility assessment, and it is also one of the most misread results in fertility medicine. The number describes something quite specific. It is routinely taken to mean something much broader.
Here is what each test measures, how they differ, and what none of them can tell you.
What ovarian reserve actually means
A woman is born with every egg she will ever have. That pool declines steadily from before birth onwards, and the decline continues regardless of whether she ovulates, takes contraception, or is pregnant. Nothing adds to it.
Ovarian reserve is an estimate of how many eggs are left in that pool. Not a count. There is no test that opens the ovary and counts, so every method is an indirect reading of something that correlates with the remaining supply.
Ovarian reserve describes quantity. It says almost nothing about quality.
That distinction does more work than any other sentence in this article. The two move on different timetables, and conflating them is where most of the distress comes from.
AMH test: what it measures
Anti-Mullerian hormone is produced by the small developing follicles in the ovary. The more of those there are, the higher the level in the blood. It is a blood test, and it can be taken on any day of the cycle, which is part of why it has become the default.
A higher AMH suggests a larger remaining pool and usually predicts a stronger response to ovarian stimulation. A lower AMH suggests a smaller pool and a more modest response.
Three things about AMH are worth knowing before you read your own result.
Units differ. AMH is reported in ng/mL in some laboratories and pmol/L in others, and the numbers look nothing alike. Comparing a result against a chart in the wrong units produces alarm out of nowhere.
Assays differ. Different laboratories use different testing platforms, and the same sample can return somewhat different values. Comparing an AMH from one lab against one from another is not strictly like for like.
Some things move it temporarily. Hormonal contraception tends to lower AMH while it is being taken, and the level typically recovers after stopping. In PCOS, AMH is often raised, because there are a large number of small follicles that are not progressing. A high AMH is not automatically good news.
Antral follicle count (AFC): counting what can be seen
The antral follicle count is an ultrasound. A transvaginal scan, usually early in the cycle, counts the small follicles visible in both ovaries. Those follicles are the ones available to be recruited that month, and the number correlates with the pool behind them.
AFC has one genuine advantage over AMH: you can see it being done, and the clinician can look at the ovaries at the same time. It also gives an immediate result rather than waiting for a laboratory.
Its weakness is that it depends on who is scanning. Counting small follicles accurately requires a good machine and an experienced operator, and two people scanning the same ovaries may not return identical numbers. It can also be harder to perform reliably in some women than others.
FSH test: the older measure
Follicle-stimulating hormone is the signal the brain sends to the ovaries to recruit a follicle. As reserve falls, the ovaries respond less readily, so the brain sends a stronger signal. A raised FSH therefore suggests the ovaries are working harder than they should need to.
It is measured on a specific day early in the cycle, usually day two or three, and it is normally taken alongside oestradiol. That pairing matters: a raised oestradiol can suppress FSH into the normal range and hide a result that would otherwise have been high.
FSH was the standard test for years and is used less now, for one main reason. It varies considerably from cycle to cycle in the same woman. A normal FSH one month and a raised one the next is a familiar pattern, and it makes any single reading hard to rely on.
It also tends to change late. FSH often stays normal until reserve has already fallen appreciably, so it is a less sensitive early signal than AMH or AFC.
AMH or AFC: which test is most useful?
In practice, AMH and AFC together. They measure the same thing by different routes, and when they agree, the picture is reasonably firm. When they disagree, that disagreement is itself informative and worth investigating rather than averaging.
FSH adds less, though it is still sometimes measured alongside the others, particularly where the clinical picture is unclear.
No single number should be treated as definitive. A result that does not fit the rest of the picture is a reason to repeat or to look further, not a conclusion.
What ovarian reserve tests cannot tell you
This is the section most often left out, and the one that matters most to the person holding the result.
They do not measure egg quality. Quality is driven overwhelmingly by age. A woman of 30 with a low AMH still has eggs of a 30-year-old. A woman of 42 with a reassuring AMH still has eggs of a 42-year-old. The tests count; they do not inspect.
They do not predict natural conception well. A low AMH tells you something about how the ovaries would respond to stimulation drugs. It is a much weaker guide to whether you will conceive without help, and it should not be read as a verdict on that.
They do not tell you when menopause will arrive. There is some association at a population level, but it is not precise enough to plan a life around.
They do not explain why conception is not happening. Ovarian reserve is one input. Tubes, the uterine cavity, ovulation itself and the male side are all separate questions, and a normal reserve result rules none of them out. A semen analysis answers a different question entirely, and it should be done alongside rather than afterwards.
What low AMH means, and what it does not
It means fewer eggs are likely to be retrieved in an IVF cycle, and the stimulation protocol may need adjusting accordingly. That is a real and useful piece of planning information.
It does not mean you cannot conceive. Women with low AMH conceive naturally, and the test was never designed to answer that question. Nor does it mean the eggs that remain are poor ones.
What it does change is the value of time. Reserve declines with age in everybody, and a result already at the lower end means there is less room to wait and see. That is worth discussing rather than ignoring, and it is a quite different conversation from the one most women have with themselves after reading a chart online.
A low result changes the timeline and the planning. It is not a diagnosis of infertility.
When ovarian reserve testing is worth doing
Ovarian reserve testing earns its place in several situations: when conception has been taking longer than expected, before starting fertility treatment so the protocol can be planned, where there is a history of ovarian surgery or treatment that may have affected the ovaries, and when considering egg freezing.
Testing out of general curiosity is a more mixed proposition. A reassuring result does not guarantee anything, and a low one in a woman not currently trying to conceive often produces considerable worry about a number that cannot answer the question she actually has.
If you do a test, have the result explained in context. The number on its own, read against a chart found online, is where almost all the unnecessary distress originates.
Frequently asked questions
What is a normal AMH level?
It depends heavily on age, and on the units and the laboratory. There is no single normal figure that applies to everyone, which is why comparing your result against a chart found online is unreliable. Ask for it to be interpreted for your age and your laboratory.
Can you get pregnant with low AMH?
Yes. AMH indicates how many eggs are likely to remain and how the ovaries would respond to stimulation. It is a weak predictor of natural conception, and women with low AMH conceive without assistance.
Can AMH be improved?
No treatment or supplement has been shown to increase the underlying egg pool. Levels can appear to shift between tests because of the assay, the laboratory, or hormonal contraception, but that is variation in measurement rather than a change in reserve.
Which is better, AMH or AFC?
Neither on its own. They measure the same thing by different routes, and used together they give a firmer picture than either alone. Where they disagree, that is worth looking into rather than averaging out.
When in the cycle should these tests be done?
AMH can be taken on any day. AFC and FSH are usually done early in the cycle, around day two or three, and FSH is normally measured alongside oestradiol.
Does a high AMH mean good fertility?
Not necessarily. A high AMH is common in PCOS, where a large number of small follicles are present but ovulation is irregular. Context matters more than the figure.
Does ovarian reserve testing tell you about egg quality?
No. These tests estimate quantity. Egg quality is determined largely by age, and there is no routine test that measures it directly.
Conclusion
Ovarian reserve testing answers one question: roughly how many eggs are likely to remain, and how the ovaries would respond if stimulated. It is genuinely useful for planning treatment.
It does not measure quality, does not predict natural conception reliably, and does not set a deadline. A low result changes the timeline and the planning rather than the outcome, and a high one guarantees nothing.
If you are holding a number you have not explained, that is the conversation worth having first.
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This article is for general information and is not a substitute for individual medical advice. Reference ranges, units and testing platforms vary between laboratories; results should be interpreted by a clinician who knows your history.