Biomarker 101: Anti-Müllerian hormone (AMH)

AMH is widely read as a fertility score. It is not one, and the distinction matters more than almost anything else on this page.

What AMH is

Anti-Müllerian hormone is produced by the small follicles in the ovaries, each containing a developing egg. The amount circulating reflects how many of those follicles are present, which is used as a proxy for ovarian reserve — the remaining pool of immature eggs.

Women are born with their full lifetime supply, roughly a million at birth, falling to around half that by puberty. Only a small fraction ever mature, typically one per cycle.

The essential limitation: AMH reflects egg quantity, not egg quality. Quality is the factor most strongly tied to age, and no blood test measures it.

What AMH does not do

AMH does not predict whether you will conceive, or how long it will take. Women with low AMH conceive naturally; women with high AMH sometimes struggle. Fertility depends on age, egg quality, tubal patency, conditions such as endometriosis, and a partner's fertility — none of which AMH addresses.

It also does not predict when menopause will occur. Levels decline as reserve falls and become very low approaching menopause, but individual variation is wide enough that AMH cannot forecast the timing.

Both of these have been marketed as things the test can do. It cannot, and understanding that before testing prevents a good deal of unnecessary distress.

Where AMH is genuinely useful

IVF planning is the clearest application. AMH helps estimate how many eggs may be retrieved in a stimulation cycle, allowing medication doses to be tailored and risks such as overstimulation anticipated.

Before cancer treatment, where chemotherapy or radiotherapy may affect ovarian reserve, AMH informs decisions about fertility preservation.

In PCOS, levels are often considerably higher than expected for age, reflecting a greater number of small follicles. It supports assessment without being diagnostic alone.

Having the test

AMH can be measured on any day of the cycle, since it does not fluctuate substantially within one — which makes it more convenient than most reproductive hormones. Values do vary between laboratories because of differing methods, so tracking over time is best done at the same laboratory.

What AMH won't tell you

• It doesn't predict conception. This is the single most important thing to understand about it.
• It doesn't predict menopause timing. Individual variation is too wide.
• It doesn't measure egg quality. Only quantity, and quality matters more.
• It isn't a general health test. Outside fertility planning, preservation decisions and specific conditions, most people have no reason to measure it.

The bottom line

AMH is a useful measure of ovarian reserve within a defined set of clinical situations, and a poor answer to the question most people bring to it. If you are trying to understand your fertility, this is one input into a fuller assessment — never a number to read on its own.