Flo Health’s mixed-methods survey of 7,640 U.S. women aged 35 and over found that 34% were unsure whether they were in perimenopause. Perimenopause is the stage when ovarian hormone production starts to fluctuate, often years before the final menstrual period, and the first changes are easy to mistake for stress, burnout or a mental health dip.
The recognition gap starts earlier than most people think
That is not a UK prevalence figure, but it does show how easily the transition is missed in women who are still well before the age many people associate with menopause.
The age stereotype is part of the problem. Menopause and perimenopause usually affect women between 45 and 55, though it can happen earlier. The British Menopause Society puts the average age of natural menopause in the UK at 51, and says the menopause transition lasts a median 7.4 years. In practice, that means symptoms can begin long before the final period and carry on for years.
What gets missed first
Perimenopause does not follow one script. Periods may become shorter, longer, heavier or more erratic. Sleep often deteriorates, mood can shift, and hot flushes or night sweats may show up. Brain fog and concentration problems are also common enough to interrupt work, home life and driving routines.
Those symptoms are easy to mislabel because they overlap with other midlife issues. Stress, thyroid problems, mental health conditions and plain overload can all produce similar complaints, which is why women often need a pattern, not a single bad week, to make sense of what is changing. Common signs include changes to periods, hot flushes, night sweats, sleep disturbance and mood changes.
Why the delay matters in day-to-day life
When women do not recognise the transition, they are less likely to seek help early and less likely to ask about treatment options. The result is often normalised symptoms that affect sleep, relationships, work performance and confidence, especially when the person assumes they are simply not coping as well as they used to.
The British Menopause Society says menopausal symptoms affect up to 80% of women.
What to track before you speak to your GP
If you think perimenopause may be starting, write down the details that show a pattern. The most useful notes are the ones that separate a one-off bad day from a hormonal shift.
- Period changes: date, length, flow, clots, skipped cycles, shorter cycles, or bleeding that is heavier than usual
- Sleep: how often you wake, whether you are drenched in sweat, and whether sleep loss is new
- Mood: anxiety, irritability, low mood, or tearfulness that feels out of step with your usual baseline
- Cognitive symptoms: brain fog, lost words, concentration lapses, or memory slips
- Temperature symptoms: hot flushes and night sweats, including when they happen and how intense they are
- Daily impact: whether symptoms are affecting work, relationships, exercise, or caregiving
That record helps because perimenopause is a diagnosis built on history and symptom pattern, not a single blood result. It also makes it easier for a GP to judge whether the symptoms fit the menopause transition or point somewhere else.
What UK guidance says about diagnosis
NICE guidance is clear: blood tests are rarely required to diagnose perimenopause or menopause in women aged over 45, and should not be taken because hormone levels fluctuate. The transition is variable, and a normal test does not necessarily explain away symptoms.
If symptoms are affecting your sleep, mood, periods or work, see your GP rather than waiting for a textbook age.
Why employers and healthcare systems are still behind
The workplace evidence shows the cost of missing this stage. A 2019 Chartered Institute for Personnel and Development survey, cited in a 2022 House of Commons Women and Equalities Committee report, found three in five menopausal women, usually aged 45 to 55, were negatively affected at work. The same report put the number of women in the UK who had left their jobs over an undefined period because of menopausal symptoms at almost 900,000.
On 2 May 2022, the Fawcett Society said a UK study based on the largest ever survey of menopausal and peri-menopausal women found many women were let down by employers and healthcare providers.