Neither a single blood test at the doctor's nor one over-the-counter kit can definitively confirm that you've reached menopause. What you can learn is whether you have an elevated FSH level at the exact time of the test. But because FSH levels fluctuate considerably during the course of a month (and because your cycles become less predictable during perimenopause), no single test can give you the whole picture. You might just happen to test on a day when your FSH is high, and it could fall again the next day. As a result, clinicians look for more than an elevated FSH level to determine whether or not you've reached menopause.