Hormones . Symptoms guide
Perimenopause: Symptoms and When to Test
Quick answer
Perimenopause is the years-long hormonal transition before menopause. Symptoms can begin in the late 30s and often overlap with thyroid disease, iron deficiency and stress. For women over 45, UK guidelines (NICE NG23) state that perimenopause should be diagnosed based on symptoms alone, as hormone levels fluctuate too wildly to provide a reliable snapshot. In this group, bloodwork is primarily used to rule out underlying mimics like thyroid dysfunction or iron depletion, rather than to gatekeep HRT. For women under 45, targeted hormone testing (especially FSH) remains a valid tool to investigate premature changes.
This patient information is being clinically reviewed by our team. The factual content draws on UK guidance (NHS, NICE, British Association of Dermatologists, and other specialist society guidance where cited).
Underlying drivers of your symptoms
- Perimenopausal hormonal change. Falling and fluctuating oestrogen, rising FSH. Note: under NICE NG23 and British Menopause Society guidance, FSH testing in women over 45 is not required to diagnose perimenopause; in women under 45, FSH is the most useful single marker. LH and oestrogen are interpreted as supporting context rather than diagnostic switches.
- Thyroid dysfunction. Symptoms overlap heavily with perimenopause; always worth checking together.
- Iron deficiency. Heavier or irregular periods deplete iron stores.
- Vitamin D deficiency. Common in women with perimenopausal mood and bone changes.
Common features that suggest this
- Irregular periods or cycle length changes
- Hot flushes or night sweats
- Sleep disruption
- Mood changes, anxiety, or low mood
- Brain fog or difficulty concentrating
- Hair thinning or skin changes
- Joint pain
Recommended tests
Same-day appointments at our Harley Street clinic, results clinician-reviewed.
Need a marker not in these panels? Build a custom panel and a GMC-registered clinician will design one for you.
Markers your clinician will commonly look at
These are the individual blood markers in the recommended panels above. Click any to read what it measures, its UK reference range, and what high or low values mean.
Testing advice
Days 2 to 5 of the menstrual cycle give the most useful baseline if cycles are still regular. If cycles are irregular or absent, any day is acceptable. Morning slot recommended. Reminder that for women over 45, NICE NG23 diagnoses perimenopause on symptoms alone; the primary value of bloodwork in this group is ruling out mimics (thyroid, iron) rather than confirming perimenopause itself.
Common questions
Can a single test confirm perimenopause?
If you are still having periods, a random blood test cannot confirm it. However, a targeted sample drawn strictly between days 2 and 5 of your cycle standardises the results. If this early follicular phase test shows an elevated FSH alongside low oestrogen, and you are experiencing matching physiological symptoms, it provides strong clinical evidence of perimenopause. For women over 45, NICE NG23 doctors still rely primarily on symptoms, but this timed baseline offers vital clarity if your presentation is complex or if you are under 45.
Will the test tell me when menopause is coming?
No test predicts the timing precisely. FSH trending up and oestrogen down suggests progression; cycle changes are usually the better indicator.
Do I need HRT?
That is an individual decision based on symptom severity, bloodwork and personal risk profile. In women over 45, NICE NG23 does not require abnormal bloodwork to start HRT. Our clinicians review your results to evaluate alternative metabolic and nutritional factors that could be compounding or mimicking your symptoms.
Related symptoms
Sources and further reading
- NICE NG23: Menopause: diagnosis and management
- British Menopause Society (BMS)
- Royal College of Obstetricians and Gynaecologists (RCOG)
This page provides general information only and is not a substitute for medical advice. A GMC-registered clinician will review your results and tailor any recommendations to you personally.