How can I find out whether I am in perimenopause?

There is no single definitive test, but a comprehensive hormone panel gives a meaningful picture. Key values are oestradiol, FSH, LH, progesterone, SHBG and thyroid function (TSH and fT4). Timing within the cycle is crucial: a measurement in the early follicular phase (days 2 to 5) gives the baseline that is easiest to interpret. A single FSH value at a random point in the cycle is often not enough, especially in early perimenopause, when hormone levels fluctuate rather than falling steadily. Your GP or gynaecologist can interpret the results in the context of your symptoms and your cycle history.