What an AMH test can and cannot tell you about fertility

What AMH is

Anti-Müllerian hormone (AMH) is produced by small follicles in the ovaries, the structures that contain developing eggs. The more of these small follicles there are, the higher the AMH level tends to be. That is why AMH is used as a marker of ovarian reserve: an estimate of the number of eggs remaining.

AMH levels fall with age, and a single blood test can be done at any point in the menstrual cycle, which makes it convenient. Those two facts explain its popularity, including in tests sold directly to consumers.

What it does well: predicting the response to IVF stimulation

In IVF, the ovaries are stimulated with hormones to produce several eggs. Knowing in advance whether someone is likely to respond weakly or very strongly helps clinicians choose a dose and avoid complications. This is the main validated use of AMH.

The UK clinical guideline on fertility from the National Institute for Health and Care Excellence (NICE, CG156) lists AMH among the tests used to predict ovarian response to stimulation, alongside the antral follicle count measured on ultrasound and FSH. As reproduced in clinical references, it describes an AMH of 5.4 pmol/l or less as suggesting a low response and 25.0 pmol/l or more as suggesting a high response (GPnotebook summary of NICE CG156). Laboratories may use different units and assays, so results must be read against the reference range of the lab that did the test.

What it does not do: predict natural fertility

The key study here was published in JAMA in 2017 by Anne Steiner and colleagues (doi:10.1001/jama.2017.14588). It followed women aged 30 to 44 with no history of infertility who had just started trying to conceive, and measured AMH and other ovarian reserve markers at the start. Of 981 women enrolled, 750 provided samples and were included in the analysis.

The finding was clear: women whose markers suggested diminished ovarian reserve were not less likely to conceive over the following months than women with normal markers. The authors concluded that their results do not support using AMH or FSH tests to assess natural fertility in women like those studied.

An earlier, much smaller study by the same group (100 women, 2011) had suggested an association, which shows why larger, prospective studies matter (see how to read a fertility study).

Why the difference?

AMH reflects the quantity of follicles, not the quality of eggs. Natural conception in a given month needs one good egg, not many. Egg quality depends strongly on age, which AMH does not measure directly. So a woman of 32 with a low AMH may conceive easily, while a woman of 42 with a normal AMH faces the decline in egg quality that comes with age.

Other situations where AMH comes up

• Egg freezing: AMH helps estimate how many eggs a cycle may yield, which is useful when deciding whether to freeze, and how many cycles may be needed (see egg freezing: what the numbers show).
• PCOS: people with polycystic ovary syndrome often have high AMH, because they have many small follicles (see PCOS explained).
• Before cancer treatment: AMH may be one of the tests used when discussing fertility preservation.

Questions to ask before paying for a test

• What decision will this result help me make?
• Who will interpret it, and against which reference range?
• Would a low result change what I do, given that it does not predict my chance of conceiving naturally?

This article summarises research and clinical guidance. It is not medical advice: a GP or fertility specialist can explain whether an AMH test is useful in your situation.

AMH and menopause

Because AMH falls as the number of follicles declines, researchers have studied whether it can predict the age of menopause. It is associated with the timing of menopause at a population level, but it cannot give an individual an exact date. The average age of menopause in the UK is 51, with wide variation; our article on when menopause happens explains what counts as early and why fertility declines years before.

Direct-to-consumer tests

AMH tests are now sold online, sometimes as "fertility MOTs" or "egg timers". A finger-prick sample is sent to a laboratory and the result comes back with a report. The measurement itself can be accurate, but the interpretation is where problems arise: a low result can cause alarm and a normal result false reassurance, when neither predicts the chance of conceiving naturally in the months ahead.

For anyone thinking about their fertility, the more useful starting points are usually age, how long they have been trying, and the general preparation set out in before trying for a baby. If there is a specific concern, a GP can arrange tests that are interpreted in context.

How results are reported

AMH results are given in different units depending on the laboratory: picomoles per litre (pmol/l), common in the UK and Europe, or nanograms per millilitre (ng/ml), common in the United States. One ng/ml corresponds to about 7.14 pmol/l, so the same result can look very different on two reports. Reference ranges also depend on age and on the assay used. This is one more reason to have a result interpreted by a clinician rather than compared with figures found online.

Used for the right purpose, in a fertility clinic planning stimulation or discussing egg freezing, AMH is a valuable test. Used as a forecast of natural fertility, it can mislead.