AMH vs FSH for Ovarian Reserve

Anti-Mullerian hormone (AMH) and follicle-stimulating hormone (FSH) are two of the most common blood tests used to estimate ovarian reserve, the pool of eggs remaining in the ovaries. They approach the question from different angles, which is why a clinician may order one, the other, or both.

What AMH reflects

AMH is produced by small developing follicles in the ovaries. Because the number of these small follicles tends to track with the size of the overall egg pool, AMH is widely used as an indirect marker of ovarian reserve. A practical advantage is that AMH stays relatively stable across the menstrual cycle, so it can usually be measured on any day rather than at a fixed point. AMH tends to decline gradually with age as the follicle pool shrinks, and it is one input clinicians use when discussing fertility expectations or planning certain treatments.

AMH does not measure egg quality, and it is not a precise predictor of whether or when someone will conceive. It estimates quantity, not the chance of pregnancy in any given month. Different laboratory assays can also report AMH on different scales, so values are best interpreted within one laboratory's method.

What FSH reflects

FSH is released by the pituitary gland to stimulate the ovaries. When the ovarian reserve declines, the ovaries respond less readily, and the pituitary often raises FSH to compensate. A higher early-cycle FSH can therefore signal a diminished reserve. Unlike AMH, FSH varies meaningfully across the menstrual cycle, so it is typically measured early in the cycle, often around day 3, and is frequently interpreted alongside estradiol because a high early estradiol can mask an elevated FSH.

FSH gives a snapshot that can vary from cycle to cycle. Because of this variability and its dependence on timing, FSH is generally considered a less stable single marker than AMH, though it remains informative, especially when read together with other results.

How the two compare

AMH and FSH look at ovarian reserve from opposite ends of the same axis. AMH is made by the ovary itself and reflects the follicle pool fairly directly, while FSH reflects how hard the pituitary is having to push the ovary. They often move in opposite directions: as reserve falls, AMH tends to decline and FSH tends to rise. Neither predicts fertility outcomes with certainty, and both are best understood as estimates rather than verdicts.

Side-by-side comparison

The table below summarizes the general differences. Descriptions are illustrative and simplified; units, assays, and reference ranges vary by laboratory and age.

For background on the hormones involved, see the hormones index; for how the samples are collected and timed, see the blood tests overview. Related conditions appear in the conditions index, and other comparisons are in the comparisons index.

Why clinicians often use both

Because each test has limitations, AMH and FSH are frequently interpreted together, sometimes alongside an ultrasound count of small follicles. Using more than one marker reduces the chance that an unusual single result is taken out of context. Even combined, these tests estimate reserve rather than predict pregnancy, and decisions about their use and meaning belong with a qualified clinician.