Perimenopause: what changes and what can be measured

The transition can be described with surprising precision. The internationally used STRAW+10 system defines stages around the final menstrual period.

• Late reproductive stage. Cycles remain regular, with initial changes in cycle length and bleeding.
• Early menopausal transition. Persistent differences of seven days or more between consecutive cycles. This marks perimenopause in the narrower sense.
• Late menopausal transition. A gap of 60 days or more without menstruation.
• Postmenopause. This begins after the final period and can only be confirmed retrospectively after twelve months without bleeding.

The practical consequence is simple: your own cycle across several months is the most informative dataset during this stage. A cycle diary or app that records bleeding, sleep, and mood provides more context than one blood draw.

In short: classification comes from the pattern over time. We therefore ask for cycle data from the previous months before the appointment.

FSH and estradiol fluctuate considerably between cycles and even from day to day during perimenopause. A result on Tuesday can look very different by Friday.

International guidelines reflect this. The NICE guideline NG23 advises clinicians to identify perimenopause or menopause clinically in women aged 45 or older with typical symptoms, using symptoms and cycle changes rather than laboratory testing. AMH, inhibin, estradiol, and antral follicle count are explicitly excluded for this purpose in this age group. FSH remains useful in defined situations: between ages 40 and 45 with relevant symptoms and below 40 when premature ovarian insufficiency is suspected. The German S3 guideline on peri- and postmenopause also centres the clinical assessment.

Laboratory testing still has a clear role during this stage. It answers other clinical questions, described below.

Reliable data is available on duration. The Study of Women’s Health Across the Nation followed 3,302 women for up to 17 years. Among women with frequent vasomotor symptoms, such as hot flushes and night sweats, the median total duration was 7.4 years. Symptoms continued for a median of 4.5 years after the final menstrual period. Women whose symptoms began early in the transition had the longest total duration, with a median above 11.8 years.

These figures change treatment decisions. A realistic view of duration helps each woman decide whether and how she wants symptoms to be treated.

In short: duration varies individually and is often longer than the commonly assumed two to three years.

Laboratory testing can identify conditions that cause or amplify similar symptoms and establish a baseline in areas where risk changes.

In practice, this includes:

• Differential diagnosis. Fatigue, sleep disruption, palpitations, and mood changes can also occur with thyroid dysfunction or iron deficiency. Heavy or prolonged perimenopausal bleeding makes iron status particularly relevant.
• Cardiometabolic baseline. Lipid profile, blood pressure, fasting glucose, and HbA1c. Cardiovascular risk changes during this stage, and a baseline provides a reference for the coming years.
• Bone health. Vitamin D, calcium, and an assessment of individual risk factors. Bone density declines fastest around the final menstrual period, making this a useful time for prevention.
• Hormone status where clinically relevant. In women below 45, with unclear symptoms, before hormone therapy, or when reviewing treatment.

Every value we request should have a defined clinical consequence.

Symptoms rarely occur in isolation. Sleep, mood, cycle, weight, libido, joints, and concentration interact, and a complete history helps identify the relevant pattern.

Our process includes cycle and symptom data submitted in advance, a 60-minute first consultation with examination, focused diagnostics with a defined question, a plan with measurable goals, and follow-up to review what has changed. Treatment options, including hormone therapy, are discussed with their benefits and risks so that the decision remains yours.

Perimenopause can be described and supported clinically, and it often lasts longer than many expect. Cycle patterns and symptoms guide classification; laboratory testing checks contributing factors and establishes a baseline for the years ahead.

If you have noticed changes over several months, a structured consultation is a useful place to begin. Bring your cycle data and existing results.