A sustained level above roughly 30 IU/L alongside twelve months without a period supports it, but the number alone is not diagnostic. In perimenopause the same woman can produce readings on both sides of that threshold within weeks.
Why it swings
Austin testing: a system in transition
An FSH number means very little without the mechanism behind it, which is where we start when a Austin patient arrives with a printout. FSH is the signal your brain sends to recruit an egg. As the ovaries become less responsive, the brain sends more, so the level rises. That part is straightforward.
What complicates it is that during perimenopause the ovaries respond intermittently. A cycle where a follicle develops produces a burst of estradiol that suppresses FSH back to premenopausal levels. The next cycle may do nothing at all.
So a woman can have genuinely menopausal-range FSH one month and a perfectly ordinary reading the next, without anything having changed about her underlying situation. More on that in hormone testing, understanding your results and estradiol go further into it. Repeat the same test at the same Austin laboratory a month later and the answer can change, which reflects the transition rather than a mistake.
