Perimenopause: What women need to know about midlife hormonal change
- Rebecca Hills
- Feb 19
- 4 min read
Updated: Mar 4
Perimenopause is a natural stage of hormonal transition, yet for many women it can feel unexpectedly disruptive.
Often described simply as the years before menopause, it is in reality a complex and highly individual phase that can last for several years.
For some, changes are subtle. For others, energy, mood, sleep and metabolism can begin to feel different in ways that are hard to explain.
This blog helps you to understand what's happening.
What is perimenopause?
Perimenopause is the transitional phase before menopause, when ovarian hormone production begins to fluctuate and eventually decline.
It typically starts in the early to mid-40s, but for some women it can begin earlier.
Menopause itself is defined retrospectively: when you've had 12 months without a period.
Perimenopause, on the the other hand, has no clear start or end point. Hormonal changes happen gradually and unevenly, which is why symptoms can come and go or change over time.
How perimenopause differs from menopause
Menopause marks the end of ovarian hormone production.
Perimenopause is characterised by unpredictability.
Oestrogen levels do not simply fall in a straight line. They often fluctuate dramatically, sometimes rising higher than pre-midlife levels before dropping again.
Progesterone, however, tends to decline earlier and more consistently.
This imbalance between oestrogen and progesterone helps to explain why perimenopause can feel so different from both reproductive years and post-menopause.
Common symptoms of perimenopause
Perimenopause can affect almost every system in the body, which is why symptoms are often wide-ranging and not always recognised as hormonally driven.
Commonly reported symptoms include:
Changes in menstrual cycle length, flow or regularity
Mood changes: often anxiety or low mood
Sleep disruption or early waking
Brain fog or reduced concentration
Fatigue and reduced resilience to stress
Weight gain or changes in body composition
Breast tenderness, headaches or joint pain
Hot flushes or night sweats
Not every woman experiences all of these symptoms, and their severity varies widely. Some notice subtle changes, others feel significantly impacted.
Why perimenopause symptoms can feel confusing
One of the challenges of perimenopause is that symptoms often don’t fit a pattern.
Hormone fluctuations can affect neurotransmitters, blood sugar regulation, inflammation and stress responses.
At the same time, midlife often brings changes in workload, caring responsibilities and sleep quality.
Because of this overlap, symptoms are frequently attributed to stress, ageing or lifestyle alone, rather than recognised as part of a hormonal transition.
Hormones do not act in isolation
Oestrogen and progesterone interact with many other hormones the body, including insulin, cortisol and thyroid hormones.
This means perimenopause can amplify existing vulnerabilities.
Stress triggers the release of cortisol, which can disrupt the body's ability to handle perimenopausal hormone changes.
Sleep disruption can worsen stress resilience.
Blood sugar instability can affect mood and energy.
Inflammation can influence joint pain and fatigue.
How perimenopause is identified in the UK
In the UK, perimenopause in women aged 45 and over is usually identified clinically based on symptoms and changes in the menstrual cycle, rather than through routine hormone blood tests.
National guidance supports this approach because hormone levels fluctuate significantly, making single blood tests unreliable.
Testing is more commonly considered in women under 45, where early menopause or premature ovarian insufficiency may need to be ruled out, or if symptoms are atypical.
When tests are performed, they may include follicle-stimulating hormone (FSH), oestradiol and sometimes thyroid function.
However, results must be interpreted cautiously. Hormone levels vary day to day and across the cycle, and a value within the laboratory reference range does not necessarily indicate stability or absence of symptoms.
Context and history remain central to understanding perimenopause.
Perimenopause as part of midlife health
During midlife, metabolic, bone and cardiovascular changes often begin to appear.
Perimenopause contributes directly to these shifts – declining oestrogen affects bone density, fat distribution, lipid profiles and insulin sensitivity.
At the same time, age, lifestyle, stress and genetics also influence how these changes unfold.
Seen in this light, perimenopause is not a problem or failure. It’s a signal that the body is adapting, and an opportunity to reflect on midlife health and lifestyle choices.
Next steps
If aspects of perimenopause feel familiar or confusing, the most helpful step is not guessing or self-prescribing solutions, but building a clearer picture of your own body.
Personalised, evidence-based support can help make sense of symptoms and create an approach that fits you.
If you’re ready to take a strategic approach to your midlife health, you can explore my 4-month Midlife Health and Ageing Strategy or book a short call to see if it’s a good fit.
Want to continue reading? Explore more articles on energy, weight changes and hormonal health – and more – in my midlife nutrition resource hub.
Disclaimer
The information and advice I provided here is of a general nature and should never replace individual health or medical advice provided by your doctor or other healthcare professional involved in your care.
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