Read this as the arc, not a single window. The early years bring subtle shifts. The mid window is where the cycle becomes irregular and the symptoms most women describe online cluster. The late window holds longer gaps between cycles. Menopause itself is the marker — twelve months without a cycle. The years after carry their own register of change. Find yourself somewhere on that arc; the rest of this page reads forward and back from where you are.

The change is rarely a single event. For most women in their early to mid forties, perimenopause arrives as a series of small recalibrations — the cycle shortens, then lengthens, then misses; mornings feel heavier; the appetite shifts; the temperature regulation that has been quietly automatic for thirty years begins to require attention.[01] The studies that follow large cohorts agree on the rough shape of the window — seven to ten years on average — but disagree, productively, on almost everything inside it.[02]

What follows is the long version of a piece we'd hand a friend who'd just asked. We've kept the compliance language honest — we are not allowed to say a supplement will improvea symptom, and we don't want to. We are allowed to describe what authorised health claims cover and what the studies actually examine, and that is what this page does.

What the research examines

Four areas of the literature are mature enough to write about with confidence for a midlife woman in the UK: magnesium and psychological function; vitamin D and bone and muscle; calcium intake thresholds; and EPA/DHA at cardiovascular doses.[03]Each has authorised wording in the GB Nutrition & Health Claims register; each has a body of trial evidence that the Cochrane and BMJ groups have reviewed. We've laid them out as numbered findings rather than bullets because the precision matters.