Perimenopause

The average UK woman starts perimenopause around age 45 and reaches menopause at 51. Some start earlier, in the late 30s or early 40s. The transition lasts on average around 4 years but commonly ranges from 2 to 8 years. Early menopause (before 45) and premature ovarian insufficiency (before 40) are clinically distinct and need specialist input.

Oestrogen and progesterone do not decline smoothly. They fluctuate erratically before settling at the lower post-menopausal levels. The fluctuations are what cause many of the symptoms, not the absolute levels themselves. FSH (follicle-stimulating hormone) rises as the ovaries become less responsive. Blood tests are not reliable for diagnosing perimenopause because levels change day to day, which is why NICE guidance prioritises symptom assessment over blood tests in women over 45.

• Period changes. Cycles become longer, shorter, heavier or lighter, often unpredictable.
• Hot flushes and night sweats.
• Sleep disturbance, particularly waking at 3 to 4 am.
• Mood changes, anxiety, lower stress tolerance.
• Brain fog and memory lapses.
• Joint aches, particularly knees, shoulders, fingers.
• Vaginal dryness and changes in libido.

Oestrogen interacts with gut motility, the gut microbiome, and the gut barrier. As oestrogen drops, gut transit can slow (more constipation), and bloating is commonly reported. Research from King's College London on the ZOE PREDICT cohort (Bermingham et al, eBioMedicine 2022) linked menopause to changes in postprandial metabolism; in that study gut microbiome richness and diversity did not differ significantly between groups, and species-level differences did not survive correction in the age-matched analysis. Women in perimenopause report new or worsening gut symptoms more often than chance suggests.

• Hormone replacement therapy (HRT). NICE recommends it as first-line for moderate-to-severe symptoms in most women without contraindications. Guidance was updated in 2024 with a shared decision-making discussion aid and a new role for CBT.
• Cognitive behavioural therapy. Evidence for reducing problematic hot flushes and night sweats.
• Strength training. Protects bone density and lean mass during oestrogen decline.
• Adequate calcium, vitamin D, and protein intake.
• Sleep prioritisation, including limiting alcohol within four hours of bed.
• Diverse plant-based fibre to support the changing microbiome.

Some symptoms attributed to perimenopause have other causes. Persistent fatigue can be iron-deficiency anaemia or thyroid disease, both more common in this age group. Sudden severe night sweats can signal infection or other conditions. Persistent heavy bleeding warrants a doctor's review. It is worth ruling out the obvious before assuming everything is perimenopausal.

Bleeding after 12 months without a period is never normal fluctuation and needs a doctor urgently. Very heavy bleeding (flooding, clots, soaking through protection hourly) deserves prompt review: it is common in perimenopause and treatable. Menopausal changes before 45, and especially before 40, deserve a doctor rather than self-management. Bloating that is there most days and does not settle should be checked whatever your age, with no age cut-off on that advice, and drenching night sweats with weight loss, fevers or new lumps are not a perimenopause pattern.