Perimenopause vs menopause: what’s actually different

Perimenopause is the years before menopause, when the ovaries’ output becomes erratic. Cleveland Clinic puts its average length at about four years (up to eight), usually starting in the mid-40s. This is where most of the symptoms live: irregular periods, hot flashes, 3 a.m. waking, brain fog, a shorter fuse, fatigue and changes in body composition.

Because hormones fluctuate rather than fall steadily, symptoms come and go — which is a big reason women doubt themselves. See perimenopause age for what’s typical when.

Menopause is defined as twelve consecutive months without a period. You only know you’ve reached it looking back. Everything after that point is postmenopause.

MedlinePlus notes that menopause before 45 is called early menopause, and before 40 premature menopause.

There’s a lot of overlap. Hot flashes and night sweats often continue past menopause — the SWAN study found they were reported most during the move from early to late perimenopause and lasted a median of 7.4 years overall. Sleep difficulties were more common in late perimenopause and postmenopause than before the transition.

What changes most is the cycle: irregular bleeding is a perimenopause feature. Any bleeding after twelve months without a period is not expected and should be checked.

Perimenopause isn’t usually confirmed by a single blood test, because hormone levels swing from day to day. UK NICE guidance says that in otherwise healthy people aged 45 and over, perimenopause can be identified from recently started hot flashes or sweats plus cycle changes — no blood test needed — and menopause from twelve months without a period (if you’re not using hormonal contraception). Under 45, tests can matter more.