The menopause series

Everything nobody told you about menopause

By Lily Niehaus, MA · Last reviewed October 2026

Most of us were taught almost nothing about this — and then expected to work, parent, and function straight through it. This section explains the physiology first, because once you understand what your hormones are doing, the symptoms stop feeling random.

Black-and-white, motion-blurred photograph of a woman holding her head — the overwhelm and brain fog many people describe in perimenopause — The overwhelm, fog and exhaustion of the transition are real physiology — not you imagining it. Photo: Anna Stampfli, Unsplash.

~51Median age of menopause in North America
12 monthsWithout a period is what defines menopauseIt is confirmed in hindsight, not by a single test.
~3.5%Of women reach menopause before 40 (POI)Higher than the 1% figure often quoted.
7.4 yearsMedian length of hot flushesNot the one or two years most people expect.

What's the difference between perimenopause, menopause and postmenopause?

Perimenopause is the transition: cycles start to change, and symptoms often begin. In the STRAW+10 staging system, early perimenopause means the length of your cycle keeps changing by 7 days or more; late perimenopause means going 60 days or more without a period. Menopause is defined in hindsight — it's the point 12 months after your final period. Postmenopause is the rest of your life after that.

Menopause before 40 is called premature ovarian insufficiency (POI). A 2024 international guideline puts it at about 3.5% of women — more than the 1% figure that is often quoted. Menopause can also be caused by surgery (removing both ovaries) or by cancer treatment; that is called induced or surgical menopause, and it starts suddenly rather than over years.

Note: cycle-based staging doesn't work the same way if you've had a hysterectomy or endometrial ablation, have PCOS or hypothalamic amenorrhea, have POI, or have had chemotherapy — your clinician will rely more on symptoms and, sometimes, tests.

Where should I start?

What sources does this page use?

Harlow SD, et al. Executive summary of the Stages of Reproductive Aging Workshop +10. Menopause. 2012;19(4):387–395. https://pmc.ncbi.nlm.nih.gov/articles/PMC3340903/
Panay N, et al. (ESHRE, ASRM, CREWHIRL, IMS). Evidence-based guideline: premature ovarian insufficiency. Hum Reprod Open / Climacteric. 2024. https://pubmed.ncbi.nlm.nih.gov/39660328/
CDC. U.S. Selected Practice Recommendations for Contraceptive Use, 2024 — when contraception is no longer needed (median age of menopause ~51). https://www.cdc.gov/contraception/hcp/usspr/contraception-not-needed.html
Avis NE, et al. Duration of menopausal vasomotor symptoms over the menopause transition (SWAN). JAMA Intern Med. 2015;175(4):531–539. https://pmc.ncbi.nlm.nih.gov/articles/PMC4433164/
NICE. Menopause: identification and management (NG23). https://www.nice.org.uk/guidance/ng23/chapter/recommendations

How should I cite this page?

Niehaus L. Everything nobody told you about menopause. The Lily Perspective. Published October 2026. Updated October 2026. https://lilyperspective.com/menopause

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