Just wanted to ad to what Daisy has shared. It is a good idea to have a series of tests over time rather than just one. While that one test for FSH levels may be accurate, chances are, it won't give you the complete and entire picture.
So many women enter perimenopause, go to their physician and have their FSH levels tested, only to be told they are "normal" and therefore they could not be in perimenopause.
this is just not true, unfortunately, and so many women are confused and frustrated. I say trust your gut and get more than just one test. It will provide a better picture of your hormonal fluctuations and improve your chances of an accurate diagnosis.
On a personal note, on the backend of my perimenopause symptoms, I suffered horribly with heavy, flooding periods with enormous blood clots.
I knew estrogen dominance was the culprit and introduced a bioidentical progesterone. It was a high quality, compounded formula with higher doses of progesterone than most (1500 mg per 2 ounces). I used it faithfully according to directions for 3 months and it knocked my heavy periods out cold.
I throw that out there as something to consider and research.