AMH (Anti-Müllerian Hormone)

What is AMH? The AMH hormone, in full anti-Müllerian hormone, is made by the cells around the smallest follicles in your ovaries. A follicle is the little sac in which an egg can mature. You are born with a fixed stock of those follicles, and that stock gets smaller throughout your life. The more small follicles still sitting in your ovaries right now, the more AMH there is to measure in your blood.

That is why AMH is used as a measure of your ovarian reserve. There is nothing complicated behind that word: it is simply an estimate of how many follicles you have left. A gynaecologist can also literally count those small sacs on an ultrasound, and the answer comes out roughly the same. An AMH blood test is the version of that count with no ultrasound attached.

The reason the test is so easy to schedule lies in where the hormone comes from. The smallest follicles grow without your pituitary driving them. FSH, LH and estradiol are driven by your pituitary and therefore swing strongly with your cycle, which is why they belong around day three. AMH barely swings at all. So you can have your blood drawn whenever it suits you, even if your cycle is irregular or you have no idea which day you are on.

What AMH does not do is look at the quality of your eggs. It is a headcount, not an inspection. Egg quality is mainly related to your age and cannot be measured with any blood test. A good-looking AMH value is therefore not a guarantee, and a low value is not a verdict.

Your result is usually given in µg/l. That number is exactly the same as ng/ml, the unit you meet in English-language articles. If your laboratory works in pmol/l, 1 µg/l corresponds to roughly 7.1 pmol/l. And never put your AMH value next to a friend's from a different laboratory: the assays are not standardised and give different numbers for the same blood.

More expectation hangs on AMH than the number can carry. Search online and you quickly read that an AMH blood test shows how much time you have left. That is not true, and you are better off knowing it before a result lands in your inbox.

Start with the bar on your result slip. For women it reads 1.00 to 13.00 µg/l. That range is not adjusted for age, and that is immediately the most misleading thing about the whole result. AMH falls throughout your life. 'Within the reference range' means something entirely different at 24 than at 41: the same 1.2 µg/l is strikingly low at 24 and completely ordinary at 41. So always read your AMH value alongside your age, never against that bar alone.

The second misconception is the biggest one. A low AMH does not mean you cannot get pregnant. In women without a fertility problem, AMH is barely related to the chance of conceiving within a year. Research among women who had only just started trying showed that a low value did not meaningfully reduce that chance. Which makes sense: as long as your cycle runs and you ovulate, one egg at a time is all you need. AMH is a number to plan with, not a countdown clock.

The third misconception: AMH does not predict when you will reach menopause. The value falls as menopause approaches, but the difference between women of the same age is so large that no year can be derived from it. Any website or test that promises you an age for your menopause on the basis of AMH is promising something your blood does not know.

So what is an AMH test actually good for? Mostly for planning. Doctors use the value to estimate how your ovaries respond to hormonal stimulation, for example in IVF or when freezing eggs: how many eggs a treatment is likely to yield, and what dose makes sense. Beyond that, a clearly low value, together with your age and your cycle, can be a reason to talk to your GP or gynaecologist sooner about wanting children. That conversation is the real yield of this test. Not the number itself.

When can you test AMH? The short answer: whenever you like. An AMH test may be done on any cycle day, you do not need to fast, and you do not need to count days. Even if your cycle is irregular or absent altogether, the result stays usable. In that respect AMH differs from almost every other female hormone.

The more interesting question is whether the test gives you anything. For most women with no complaints and no concrete plans for children, an AMH value does not: you get back a number that leads to no action, and sometimes a scare that rests on nothing. Testing is worthwhile when conceiving is taking longer than you expected, when you are thinking about freezing eggs, when your cycle has been irregular or absent for months, and before or after ovarian surgery.

With an irregular cycle, incidentally, your GP rarely looks at AMH alone. An underactive thyroid or a raised prolactin can throw a cycle off just as easily, so TSH and prolactin often go along in the same blood draw.

Do you use the pill, an implant or a ring? Always flag it with your result. Combined hormonal contraception pushes AMH down by roughly a quarter on average, so your result then underestimates your true reserve. The effect is reversible: after stopping, the value usually recovers within a few months. Never stop your contraception on your own initiative just to have a blood value measured. Discuss that with your GP first.

And how fast does your AMH value actually fall? Gradually, and fastest after thirty. As orientation, and explicitly not as a cut-off: the median sits at roughly 3.3 µg/l around 25, roughly 1.4 µg/l around 35 and roughly 0.5 µg/l around 40. The spread within any age is enormous, and these figures come from one specific assay, so your laboratory may work with different numbers. Use them to place a result, not to give yourself a score.