In short: perimenopause has four stages. The late reproductive years are the quiet lead-up, early perimenopause is when your cycle starts to shift, late perimenopause is when periods begin to skip, and postmenopause begins a full year after your last period. Most women enter it in their mid-40s, though it can start in the late 30s, and the whole transition can last anywhere from a few months to more than ten years.
First, what is actually happening
To make the stages make sense, it helps to know the one change underneath all of them.
Your ovaries hold a set number of eggs, and releasing an egg each month is what drives your cycle. As you move into your forties, the ovaries start running low, and they stop working as smoothly as they used to. The hormone at the centre of this is oestrogen, the main female hormone your ovaries produce. Oestrogen does far more than run your periods. It affects your sleep, your mood, your body temperature, your memory, even your heart and bones. So when it changes, you can feel it in places that seem to have nothing to do with periods at all.
Here is the key thing, and it surprises most women: in perimenopause, oestrogen does not simply drop in a straight line. It swings. Some days it is high, some days it is low, and it lurches between the two. Think of a dimmer switch that flickers before it finally dims, rather than a light being turned off. That flickering is why the symptoms come and go, why one week can feel fine and the next does not, and why it can be so hard to pin down.
Doctors have mapped this whole process into stages, using a system called STRAW (you do not need to remember the name). We will use those same stages here, in everyday language.
The four stages at a glance
| Stage | Typical age | What is happening | What you might notice |
|---|---|---|---|
| The lead-up (late reproductive years) | Your forties | Ovaries begin to slow; hormones still fairly steady | Little or nothing; maybe slightly shorter cycles |
| Early perimenopause | Mid-to-late forties | Oestrogen starts to swing | Cycle length shifts by a week or more; first hot flushes, poorer sleep |
| Late perimenopause | The one to three years before your last period | Bigger hormone swings, then a downward trend | Skipped periods, gaps of 60+ days; symptoms often peak |
| Postmenopause | From one year after your last period | Oestrogen settled low and steady | Many symptoms ease; bone and heart health matter more |
Remember, these ages and lengths are typical, not fixed. Your own timing may be quicker or slower, and that is normal.
The lead-up: your late reproductive years
Roughly your forties, before anything obvious changes.
This is the quiet, early stage, and most women do not know it is happening at all. Your periods are still regular, or nearly so. Behind the scenes, though, your ovaries are beginning to slow, and your body responds by working a little harder to keep your cycle going.
You might notice your periods arriving slightly closer together, or you might notice nothing. Both are completely normal. There is nothing to fix here. The one genuinely useful thing at this stage is simply to get a feel for what is normal for you: how you usually sleep, how your energy sits, what your cycle usually does. That personal baseline becomes the thing later changes stand out against.
Early perimenopause
Your mid-to-late forties, when the changes become noticeable.
This is the stage where you start to see it on the calendar. The clearest sign is that your cycle length shifts by a week or more and stays that way, so a period that always came at 28 days now turns up at 36, or comes early. This is the point most women realise something is genuinely changing.
This is also when the more familiar symptoms often begin. Around four in ten women get hot flushes by this stage, and disrupted sleep and mood dips are common too. If it feels like several unrelated things going wrong at once, that is the oestrogen swings showing up in different parts of your body. It is one cause, not five. anna's symptoms guide walks through the ones that are easy to miss or blame on something else.
Late perimenopause
Usually the one to three years before your last period.
Now the changes are hard to ignore. Your periods start skipping. You might go 60 days or more without one, then have one, then skip again. The gaps get longer and more unpredictable.
This tends to be the most up-and-down stretch, because your oestrogen is swinging at its widest before it finally settles at a lower level. Hot flushes and night sweats are usually at their most noticeable here, affecting most women in this stage. Because your body can feel genuinely unpredictable day to day, the thing that helps most is watching the overall trend across weeks, rather than reading too much into any single rough day.
Postmenopause
From one year after your final period onwards.
Here is something that catches everyone out: you cannot know the exact day of your last period until a full year has passed with no more bleeding. Only then is it official, looking back. Everything after that year is called postmenopause.
In the first handful of years, your oestrogen has settled at a low, steady level rather than swinging, and for many women the hot flushes gradually ease (though for some they linger). This is the stage to gently shift your attention to the long game. Oestrogen quietly protected your bones and your heart for decades, so with less of it around, looking after both becomes more worthwhile than ever.
How long does each stage last?
There is no fixed length for any single stage, and this is where women differ the most. One woman might sit in the early stage for years and pass through the late stage quickly, while another does the complete opposite. There is no set speed, and moving through fast is just as normal as taking your time. Taken together, perimenopause lasts around four years for a lot of women, but it honestly ranges from a few months to more than ten, and the average age of reaching menopause is 51. You only ever know your own length once it is behind you. We go into what makes it longer or shorter, and how you tell it is ending, in how long does perimenopause last.
The takeaway is simple: the stage you are in tells you far more than your age does. Two women who are both 47 can be in completely different stages, and moving at completely different speeds. So rather than counting down to some finish line, the more useful question is what your body is doing right now.
How to tell which stage you're in
You might assume a blood test would just tell you. Sadly, during perimenopause it usually cannot, and it is worth knowing why so you are not caught out. Because your hormones swing so much from week to week, a blood test only captures one moment. It might look completely normal one day and clearly menopausal a few days later, so a single result cannot reliably place you.
The better guide is your own pattern. For most women over 45, doctors do not use blood tests at all. Irregular periods plus the familiar symptoms are enough. The signals worth watching are your own: how your cycle is changing, how your sleep is holding up, and how things like your body temperature and resting heart rate are drifting across the weeks and months.
One thing to flag, because it matters: if symptoms start before 45, or if you have any bleeding after a full year with no periods, book a chat with your doctor. Those are worth checking. anna does not diagnose, and this page is not medical advice, it is here to help you understand what is happening. If treatment comes up in that conversation, our plain-English overview of HRT in perimenopause explains the options.