Perimenopause is not menopause
Menopause is a single day — the 12-month anniversary of your last period. Everything before that is perimenopause: the years-long transition when ovarian function is winding down.
The average age of menopause in the UK is 51, but perimenopause commonly starts in the mid-40s, and can begin in the late 30s. Early menopause (before 45) affects around 5% of women; premature ovarian insufficiency (before 40) affects around 1%.
What actually changes
- Cycle length becomes unstable
- Cycles get shorter, then longer, then unpredictable, as ovulation becomes intermittent.
- Estrogen fluctuates wildly
- Not a smooth decline — it swings high and low, which is why symptoms can feel worse than in full menopause.
- New symptoms appear
- Hot flushes, night sweats, sleep disruption, brain fog, joint aches, anxiety, low mood, changes in libido and skin.
- Bleeding pattern changes
- Heavier bleeds, spotting between periods, or missed periods are common — but always worth flagging to a GP.