Perimenopause is the time around the transition to menopause, but its exact starting point depends on how the term is used. The STRAW+10 system, widely used in research, stages the menopausal transition by changes in menstrual cycles. The early transition begins when the length of consecutive cycles differs by at least seven days and this pattern recurs. The late transition includes a gap of at least 60 days without a period. Menopause itself is confirmed retrospectively, after 12 months without menstruation.
In clinical care, the picture can be less clear-cut. Some women experience symptoms such as hot flushes, disrupted sleep or mood changes before their cycles meet the STRAW+10 criteria. Others may be unable to track cycle changes because they have had a hysterectomy or use hormonal contraception. A clinician therefore considers age, symptoms, menstrual and medical history, and whether another condition could explain what is happening.
For most women aged 45 or over with a typical history, a blood test is not needed to identify perimenopause. Follicle-stimulating hormone (FSH) levels can fluctuate, so one result cannot reliably confirm or rule it out. Testing may be helpful in selected circumstances, particularly when menopause is suspected before age 45 or premature ovarian insufficiency is suspected before age 40.
The practical message: you do not need to wait until you have missed periods for new symptoms to be taken seriously. Equally, symptoms should be assessed in their wider health context rather than automatically attributed to perimenopause.
References:
Harlow, S. D., Gass, M., Hall, J. E., Lobo, R., Maki, P., Rebar, R. W., Sherman, S., Sluss, P. M., de Villiers, T. J., & Group, S. C. (2012). Executive summary of the Stages of Reproductive Aging Workshop + 10: addressing the unfinished agenda of staging reproductive aging. The Journal of Clinical Endocrinology & Metababolism, 97(4), 1159-1168. https://doi.org/10.1210/jc.
Lumsden, M. A., Dekkers, O. M., Faubion, S. S., Linden Hirschberg, A., Jayasena, C. N., Lambrinoudaki, I., Louwers, Y., Pinkerton, J. V., Sojat, A. S., & van Hulsteijn, L. (2025). European society of endocrinology clinical practice guideline for evaluation and management of menopause and the perimenopause. European Journal of Endocrinology, 193(4), G49-G81. https://doi.org/10.1093/
Panay, N., Fenton, A., Hamoda, H., Hillard, T., Islam, R., Pedder, H., Romero, L., Vincent, A. J., & Group, I. M. S. R. W. (2025). International Menopause Society (IMS) recommendations and key messages on women’s midlife health and menopause. Climacteric, 28(6), 634-656. https://doi.org/10.1080/
