What Happens During Perimenopause: Symptoms, Timeline, and What to Expect

During perimenopause, your body gradually produces less oestrogen and progesterone as your ovaries begin winding down — a transition that can last anywhere from two to twelve years before your periods stop entirely. This hormonal shift triggers a wide range of physical and emotional changes, from irregular periods and hot flushes to sleep disruption and mood changes, all of which vary considerably from person to person.

This is not medical advice. Always consult your GP or a qualified menopause specialist about your individual symptoms and circumstances.

What Happens During Perimenopause: The Hormonal Shift Explained

Perimenopause literally means "around menopause." According to the NHS, it is the transitional stage that begins when the ovaries gradually start producing less oestrogen, and it ends twelve months after your final period — at which point you have reached menopause. The years after that are known as postmenopause.

The driving force behind perimenopause is a decline in ovarian function. Your ovaries have been releasing eggs since puberty, and as your egg supply diminishes, levels of two key hormones — oestrogen and progesterone — begin to fluctuate unpredictably. The hypothalamus, which regulates body temperature among many other functions, is particularly sensitive to falling oestrogen levels. This is why thermoregulation becomes disrupted, leading to the hot flushes and night sweats that many people associate with this life stage.

Follicle-stimulating hormone (FSH) rises during this period as the body attempts to compensate for declining ovarian output. A blood test measuring FSH levels can sometimes help confirm perimenopause, though the NHS notes that because hormone levels fluctuate so dramatically, a single test is rarely conclusive. NICE guideline NG23 on menopause specifically recommends that diagnosis should primarily be based on symptoms in women aged 45 and over, rather than on blood tests alone.

What age does perimenopause start? According to the NHS, most people begin perimenopause in their mid-to-late forties, though it can start as early as the late thirties for some. The average age of menopause in the UK is 51, meaning perimenopause often begins somewhere in the mid-to-late forties. Premature ovarian insufficiency (POI) affects around 1 in 100 women under the age of 40.

The Most Common Symptoms of Perimenopause

Perimenopausal symptoms vary widely in type, timing, and severity. Some people sail through with minimal disruption; others find their daily lives significantly affected. NHS guidance identifies the following as the most frequently reported symptoms:

It is important to note that not all of these symptoms will affect every person, and many may be barely noticeable. According to menopause specialists, symptoms typically peak in the late perimenopause stage and often improve after menopause is reached.

How Perimenopause Affects Your Periods

One of the earliest and most reliable signs that perimenopause has begun is a change in your menstrual cycle. During your reproductive years, cycles follow a broadly predictable pattern. In perimenopause, this regularity begins to break down as ovulation becomes less consistent.

You might notice cycles shortening first — common in early perimenopause — before becoming longer and more erratic in the later stages. Heavy periods (menorrhagia) are also common, and the NHS advises speaking to a GP if bleeding becomes very heavy, lasts longer than seven days, or occurs between periods, as these symptoms can occasionally indicate other conditions that require investigation.

Spotting between periods can happen during perimenopause due to hormonal fluctuations, but it should always be assessed by a healthcare professional to rule out other causes. NICE guidance recommends that any postmenopausal bleeding — defined as bleeding that occurs twelve or more months after your last period — should be investigated promptly.

Can you get pregnant during perimenopause? Yes. Until you have gone twelve consecutive months without a period (which marks the official point of menopause), pregnancy remains possible. NHS guidance advises continuing to use contraception throughout perimenopause until you have reached menopause, as ovulation can still occur even when periods are irregular.

What Happens During Perimenopause to Your Mental Health

The psychological impact of perimenopause is frequently underestimated — both by those experiencing it and by healthcare professionals. Oestrogen plays a significant role in regulating mood, partly through its influence on serotonin and dopamine, the neurotransmitters most closely associated with wellbeing and motivation. As oestrogen levels fluctuate and eventually fall, these mood-regulating systems become less stable.

According to research published in Archives of General Psychiatry, women in the perimenopausal transition are two to four times more likely to experience a major depressive episode compared to the premenopausal period. This elevated risk is particularly pronounced in those who have previously experienced premenstrual syndrome (PMS), postnatal depression, or prior episodes of depression.

Anxiety is another commonly reported but frequently unrecognised symptom. People describe a new or worsening sense of worry, a feeling of dread, or a heightened stress response that feels out of proportion to their circumstances. Cognitive symptoms — including forgetfulness, word-finding difficulties, and difficulty concentrating — are also frequently reported, though research from the SWAN study suggests these tend to improve after the menopause transition is complete.

It is also worth acknowledging the psychological dimension of the transition itself. Perimenopause often coincides with significant life events — children leaving home, career pressures, caring for ageing parents, relationship changes — and the physical symptoms of perimenopause can interact with these stressors in complex ways.

If you are experiencing low mood, anxiety, or significant mood changes, speak to your GP. Effective support is available, including hormone replacement therapy (HRT), cognitive behavioural therapy (CBT) — which NICE guideline NG23 specifically recommends for psychological symptoms associated with menopause — and other targeted interventions.

Tracking What Happens During Perimenopause: Why It Matters

One of the practical challenges of perimenopause is that its symptoms are so varied and fluctuating that they can be difficult to communicate to a healthcare provider, or even to recognise as connected to hormonal changes at all. A person experiencing anxiety, joint pain, and poor sleep simultaneously might not immediately link these to perimenopause — particularly in their early-to-mid forties when the transition is less expected.

This is where symptom tracking becomes genuinely valuable. Keeping a detailed log of your symptoms — their frequency, severity, timing, and any apparent triggers — gives you and your doctor a much clearer picture of what you are experiencing. It can help confirm whether symptoms follow a cyclical hormonal pattern, assess whether a treatment (such as HRT) is working, and identify specific triggers for symptoms like hot flushes or sleep disruption.

Flarewise, the menopause symptom tracker developed by TenderLab, is designed specifically for this purpose. It allows you to log over 40 symptoms associated with perimenopause and menopause, track patterns over time, and generate reports you can share with your GP or menopause specialist. Flarewise is a tracking tool, not a diagnostic device — but it can provide the kind of detailed, longitudinal data that makes clinical conversations more productive and helps you feel more informed and in control.

Research supports the value of this kind of self-monitoring. A 2020 review in the journal Maturitas noted that patient-reported outcomes — including symptom diaries — improved communication between patients and clinicians in menopausal care, leading to more personalised and effective treatment decisions.

Long-Term Health Changes to Be Aware Of During Perimenopause

Beyond the day-to-day symptoms, perimenopause marks the beginning of a longer-term shift in health risk profile that is important to understand. As oestrogen levels decline, several aspects of physical health become more vulnerable:

None of this is intended to be alarming. Awareness of these changes creates an opportunity to take proactive steps — through diet, exercise, not smoking, limiting alcohol, and discussing HRT and other options with your GP — that can significantly reduce long-term health risks.

When to Seek Medical Support

NHS guidance recommends speaking to your GP if perimenopausal symptoms are affecting your quality of life. There is no need to simply endure significant disruption — effective treatments and support are widely available. You should seek prompt medical advice if you experience:

NICE guideline NG23 sets out a clear framework for the diagnosis and management of menopause in the UK, and the British Menopause Society publishes regularly updated guidance for healthcare professionals. If you feel your symptoms are not being taken seriously, you are entitled to ask for a referral to a specialist menopause clinic.

Frequently Asked Questions About Perimenopause

How long does perimenopause last?

According to the NHS, perimenopause typically lasts between two and twelve years, though the average duration is around four to eight years. The length of the transition varies considerably between individuals and is influenced by factors including genetics, smoking status, and overall health. Perimenopause ends twelve months after your final menstrual period.

What are the first signs that perimenopause has started?

The earliest signs of perimenopause often include changes to your menstrual cycle — cycles that become shorter, longer, or more irregular than usual. You may also notice increased premenstrual symptoms, mild hot flushes, sleep disturbances, or mood changes. According to NHS guidance, these early changes most commonly appear in the mid-to-late forties.

Can perimenopause cause anxiety?

Yes. Anxiety is a recognised and common symptom of perimenopause, linked to hormonal fluctuations affecting neurotransmitter systems that regulate mood. According to NICE guideline NG23, cognitive behavioural therapy (CBT) is an evidence-based treatment for anxiety associated with the menopause transition, and HRT may also help in appropriate cases. Always speak to your GP about significant anxiety symptoms.

Is perimenopause the same as menopause?

No. Perimenopause is the transitional phase leading up to menopause, during which hormone levels fluctuate and symptoms typically emerge. Menopause itself is a single point in time — defined as twelve consecutive months without a menstrual period. The years following that point are known as postmenopause. In everyday conversation, "menopause" is often used loosely to describe the entire transition.

How can I tell if my symptoms are perimenopause or something else?

Many perimenopausal symptoms — including fatigue, mood changes, weight changes, and sleep problems — overlap with other conditions such as thyroid disorders, anaemia, or depression. According to NICE guideline NG23, diagnosis in women over 45 should be based primarily on symptoms, but your GP may recommend blood tests to rule out other conditions. Detailed symptom tracking over time can provide valuable information to support this process.

Start Tracking Your Perimenopause Symptoms with Flarewise

Understanding what happens during perimenopause is the first step — but tracking your own experience is what puts you in a stronger position to seek the right support. Flarewise, TenderLab's dedicated menopause symptom tracker, helps you log your symptoms day by day, spot patterns over time, and build a clear picture of your own perimenopausal journey to share with your healthcare team.

Flarewise is not a diagnostic tool, and it is not a substitute for medical advice — but it is a genuinely useful companion through one of the most complex and variable health transitions of your life. Take the guesswork out of your appointments and start tracking your symptoms today.

This article is for informational purposes only and does not constitute medical advice. If you are concerned about symptoms of perimenopause or any other health condition, please consult your GP or a qualified healthcare professional.