AMH: what it says about fertility, and what it does not

Anti-Müllerian hormone, or AMH, has become one of the most talked about fertility tests. It is sometimes described as an “egg timer” test, which makes it sound more precise than it is. AMH can answer one question quite well. It cannot answer several others that people often hope it will.

AMH is not part of the standard Well Woman panel. It is available as an add-on for women with fertility or perimenopause questions.

What AMH measures

You are born with all the eggs you will ever have, and the number falls steadily over the years. At any time, a group of eggs is in the early stages of growing inside small follicles in the ovaries. The cells around these follicles make AMH. The more small follicles there are, the higher the AMH.

This makes AMH a marker of ovarian reserve, meaning roughly how many eggs remain. It is highest in young adulthood and falls with age, becoming very low as menopause approaches. Because it reflects a steady population of follicles, AMH changes much less across the cycle than FSH or oestradiol, so it can usually be tested on any day.

What AMH does not measure

• Egg quality. The chance that an egg is healthy depends mainly on your age, not your AMH. A 30 year old with a low AMH generally has better quality eggs than a 42 year old with a high one.
• Your chance of natural conception. Studies of women without known fertility problems who were trying to conceive naturally found that AMH did not predict how quickly they fell pregnant. A low AMH does not mean you cannot conceive, and a high AMH does not mean you will conceive easily.
• The exact timing of menopause. Low AMH suggests fewer eggs remain, but it cannot tell an individual woman when her periods will stop.
• Whether your tubes are open, whether you ovulate, or anything about sperm, all of which matter as much to fertility.

Where AMH is genuinely useful

AMH is most valuable in fertility clinics. It helps predict how the ovaries will respond to stimulation medicines during IVF or egg freezing, which guides the treatment plan. A very low result can mean fewer eggs are likely to be collected. A very high result can signal a higher risk of over-response.

Outside the clinic, AMH can help a woman who wants to understand her options, for example when thinking about the timing of a family or whether to see a fertility specialist sooner rather than later. It is also one of the findings that can support a diagnosis of polycystic ovary syndrome, where AMH is often high because there are many small follicles.

Things that change AMH

• Age, by far the biggest factor.
• Hormonal contraception, which can lower AMH temporarily. The level usually recovers after stopping.
• PCOS, which tends to raise it.
• Ovarian surgery, chemotherapy and some other treatments, which can lower it.
• The lab method. AMH assays are not fully standardised, so results from different labs are not always directly comparable.

Because of this, and because what counts as low changes with age, we do not quote a single AMH range. Your result is read against the lab's age-related range and the rest of your picture.

How AMH fits with the rest of your results

AMH is most informative alongside FSH and oestradiol from early in the cycle, your age, and your period history. A low AMH with a high early-cycle FSH points more strongly to reduced reserve than either result alone. In a woman under 40 with irregular or missed periods, that combination needs a doctor's review.

When to see a doctor

General advice is to see a doctor if you are under 35 and have not conceived after a year of trying, or after six months if you are 35 or older. Go sooner if your periods are irregular or absent, or if you or your partner have a known fertility concern. A low AMH is a reason to have that conversation earlier, not a reason to panic.

Your LifePrint report explains what your AMH suggests and what it cannot show. Decisions about fertility treatment or egg freezing belong with a registered healthcare practitioner or fertility specialist who can look at the whole picture.