What's the difference: perimenopause vs menopause?

The simplest way to remember it: perimenopause is the years-long transition leading up to menopause, and menopause is a single point in time, the day you have gone 12 months without a period.

Perimenopause, meaning "around menopause", is the run-up, often starting in your forties (sometimes the late thirties) and lasting anywhere from a couple of years to a decade. Your hormones, especially oestrogen and progesterone, fluctuate erratically, which is why this stage causes most of the well-known symptoms: irregular periods, hot flushes, broken sleep, mood swings and brain fog. Crucially, you are still having periods and can still get pregnant.

The three stages line up like this:

• Perimenopause — the symptom-heavy transition, hormones swinging, periods still happening
• Menopause — technically one day, marked once you have had no period for 12 straight months (average age around 51)
• Post-menopause — everything after, when hormone levels settle at a new, lower baseline

Confusingly, most people say "menopause" loosely to mean the whole experience, but medically the distinction matters, because the unpredictable, symptom-heavy phase is usually perimenopause rather than menopause itself. It matters practically too: you can still conceive during perimenopause, so contraception is still relevant, and the erratic hormone swings of this phase often need a different approach from the steadier low levels of post-menopause. Knowing which stage you are in, explained further in how to tell if you are in perimenopause, shapes what help makes sense.

What to do: if you are in your forties with changing periods and new symptoms, you are most likely in perimenopause, and you do not have to wait until periods stop to get help. Treatments and lifestyle changes, including HRT, work during the transition, not just after it. Tracking your cycle and symptoms gives you and your doctor a much clearer picture of where you are.