Perimenopause is the transitional phase before menopause, when hormone levels begin to fluctuate rather than simply decline. It typically begins in the mid-forties, with a median onset around age 45 and a normal range spanning the early forties to early fifties. It usually lasts between four and eight years.
Those are the averages. The more useful point is that the range is wide, the first symptoms are often not the recognisable ones, and a great many women spend years in perimenopause without anyone naming it.
I should say at the outset that this is not only a clinical interest of mine. Perimenopause arrived for me in my early forties, and it did not announce itself with hot flushes. It began with brain fog – I could not think clearly, and I did not feel like myself.
Even with twenty years of clinical experience, I found it difficult to be taken seriously. Which made me think rather a lot about the women in my own waiting room, with no medical background and nobody in their corner.
Dr Katy Kasraie, BMS-accredited Menopause Specialist
What Is Perimenopause?
Perimenopause is the phase that precedes menopause, driven by the natural decline in ovarian function. Oestrogen and progesterone production becomes erratic before it falls away, which is why symptoms can come and go rather than build steadily.
Menopause itself is diagnosed retrospectively, once twelve consecutive months have passed without a period. In the UK the average age is around 51.
One important distinction: when ovarian function ceases before the age of 40, this is premature ovarian insufficiency rather than early perimenopause. It is a separate diagnosis, it is investigated differently, and it warrants specialist input – so it is worth naming clearly rather than folding into the same conversation.
Common symptoms
Over thirty symptoms are recognised. Hot flushes are simply the most talked-about.
Cognitive
Brain fog, difficulty concentrating, memory lapses, word-finding difficulty, a sense of not feeling like yourself
Mood
New or worsening anxiety, low mood, irritability, mood swings, reduced confidence
Sleep
Waking in the early hours, difficulty falling asleep, night sweats, unrefreshing sleep, persistent fatigue
Physical
Irregular or heavier periods, hot flushes, joint pain and stiffness, palpitations, weight change, headaches
Intimate & bladder
Vaginal dryness, discomfort during sex, reduced libido, urinary urgency, recurrent urinary tract infections
You do not need hot flushes to be in perimenopause. For many women, sleep or mood changes come first.
Published estimates suggest between 59 and 65 per cent of women experience vasomotor, psychological or urogenital symptoms during this transition. Severity varies enormously, and symptoms that seem unrelated frequently turn out to share the same cause.
What influences when it starts?
Family history
The age at which your mother or sisters went through menopause is one of the better available guides.
Smoking
The most consistently established lifestyle factor. Pooled analyses of large cohort studies show smokers reach menopause on average around a year earlier than non-smokers.
Medical treatment
Chemotherapy, radiotherapy, and surgery involving the ovaries can bring on menopause abruptly, sometimes many years early.
Health conditions
Certain autoimmune conditions can affect ovarian function. NICE also notes that women from some ethnic minority backgrounds, and those with some lifelong conditions, may experience menopause younger.
Body weight
Often cited, but the evidence here is genuinely mixed and not yet settled - large reviews have reached differing conclusions, complicated by smoking as a confounding factor.
How is it diagnosed?
This is where a great deal of unnecessary confusion arises, so it is worth being precise.
In women aged 45 and over, perimenopause is diagnosed from symptoms and menstrual pattern alone. NICE guidance is explicit that hormone blood tests should not be used to identify perimenopause or menopause in this age group – including oestradiol, anti-Mullerian hormone, inhibin A and inhibin B – because levels fluctuate substantially and a result within the normal range tells you very little.
FSH testing has a narrower role. It may be considered in women aged 40 to 45 who have symptoms including a change in their cycle, or in women under 40 where menopause is suspected.
Other blood tests are still worth doing, but for a different reason: to rule out conditions that mimic perimenopause. Thyroid function, a full blood count, ferritin, vitamin B12 and vitamin D deficiency can all produce fatigue, low mood and poor concentration. Treating those makes a real difference – they simply do not confirm or exclude perimenopause.
If you have been told your bloods are normal but you know something is not right – that is a recognised situation, not a contradiction. A normal result does not mean you are imagining it. It means the test has limits.
Treatment options
Perimenopause is a natural phase, not an illness. But symptoms that interfere with sleep, work, mood or relationships are worth treating, and there is usually a good deal that can be done.
Hormone replacement therapy remains the most effective treatment for vasomotor symptoms, and for many women improves sleep, mood and concentration alongside. Where suitable, transdermal oestrogen with body-identical micronised progesterone is prescribed, dosed individually and reviewed regularly.
Non-hormonal options matter for women who cannot take HRT, or would rather not – including those with a history of hormone-sensitive breast cancer. Several medications are used in this setting, though it is worth knowing that some are prescribed off-label, as they are not licensed in the UK specifically for menopausal symptoms. NICE advises against routinely offering SSRIs or SNRIs as a first-line treatment for hot flushes alone. Which option suits you is an individual decision, made together.
Local treatments for vaginal dryness, discomfort and urinary symptoms are safe for long-term use and highly effective. These symptoms are among the most under-reported and the most treatable.
Lifestyle measures genuinely help rather than merely being something to say. Resistance training, adequate protein, attention to sleep, and reducing the cortisol load where possible all support how you feel – and protect bone, muscle and cardiovascular health for the decades ahead.
Some women also find complementary approaches helpful. If you are considering herbal products, do mention them – several interact with prescribed medication, and preparations vary considerably in dose and purity.
What happens afterwards?
Once twelve consecutive months have passed without a period, you have reached menopause, and natural conception is no longer possible. Until that point it is – so contraception is generally advised until the age of 55.
Postmenopause brings its own considerations. Cardiovascular risk rises as oestrogen falls, bone loss accelerates, and metabolic changes become more pronounced. This is not cause for alarm; it is the argument for looking ahead. The decisions that shape health in your seventies are largely made in your forties and fifties.
Frequently asked questions
At what age does perimenopause usually begin?
Most commonly in the mid-forties, with a median onset around 45 and a usual range from the early forties to the early fifties. Ovarian function ceasing before 40 is premature ovarian insufficiency, which is a distinct diagnosis.
What are the first signs?
Frequently not the ones people expect. Changes in cycle length, disrupted sleep, new anxiety and difficulty concentrating often appear before hot flushes, and often before periods become noticeably irregular.
My GP said my bloods were normal. Can I still be perimenopausal?
Yes. In women over 45, perimenopause is a clinical diagnosis based on symptoms and timing, and NICE advises against using hormone tests to make it. Levels fluctuate, sometimes within a single day. A normal result does not rule anything out.
How long does perimenopause last?
Typically four to eight years, though it can be shorter or considerably longer. Most people underestimate it.
Can I get pregnant during perimenopause?
Yes – ovulation still occurs, if unpredictably. Contraception is generally advised until age 55, or until menopause is confirmed.
Should I see a specialist?
Many women are managed well in primary care. A specialist is worth considering if symptoms are not improving, if HRT has been prescribed but is not working, if you have a complicating history such as previous breast cancer, or if you would simply like more time than a standard appointment allows.