What is perimenopause?

Your symptoms are real — and you're not alone in this.

Perimenopause is the transitional period before menopause. This phase can last 5 to 10 years and often begins between ages 40 and 50. It's a period during which your body gradually prepares for a new hormonal balance.

Although you're still menstruating, you may already experience symptoms similar to those after menopause. This can be confusing — and sometimes frightening — especially if you don't know where they're coming from.

How do you recognize perimenopause?

It's often a combination of signals, such as:

Changes in your menstruation (irregular, skipped, shorter or heavier than before)
New symptoms you didn't have before
Symptoms that come in waves (periods when things are fine, alternating with weeks or months when it's more difficult)

Because hormones fluctuate strongly during this phase, a blood test is often not a reliable indicator of how you feel.

The different phases at a glance

Perimenopause: transitional phase, menstruation is still present
Menopause: you haven't had a period for 12 months
Post-menopause: the period after that

Why are symptoms sometimes cyclical and sometimes irregular?

During perimenopause, the function of your ovaries gradually changes. How many symptoms you experience — and whether they're predictable — depends on your ovarian reserve.

What is ovarian reserve?

This is the number and quality of the remaining follicles in your ovaries. These follicles contain the eggs and are responsible for hormone production.

Higher reserve → more follicles respond to FSH
Lower reserve → fewer and variably responding follicles

(FSH is the signal your brain sends to your ovaries and can be measured in blood.)

Early perimenopause – often still recognizable and cyclical

In this phase:

There are still enough follicles
Ovulation often still occurs
Symptoms often return monthly

What happens hormonally?

FSH rises slightly
Estrogen can peak (sometimes even higher than before)
Progesterone is often lower due to cycles without ovulation

What might you feel?

Tender or painful breasts
Headaches or migraines
Irritability or feelings of anxiety
Heavier or longer periods

The symptoms of progesterone deficiency are often most noticeable:

Poor sleep
Mood swings
Inner restlessness

Late perimenopause – more unpredictable

When the ovarian reserve decreases further:

Sometimes no follicle matures
Sometimes one (or more) follicle(s) react extremely
There are many cycles without ovulation

What happens hormonally?

Estrogen production becomes unpredictable
Progesterone is often absent
FSH fluctuates strongly

What might you feel?

With low estrogen levels:

Hot flashes (or general feeling of warmth) and night sweats
Heart palpitations
Feelings of anxiety or panic
Fatigue

With strongly fluctuating estrogen levels:

Mood instability
Irritability
Less stress resilience

Due to progesterone deficiency:

Difficulty falling asleep
Waking up at night
Worsening of anxiety feelings

Often these symptoms overlap, making it unclear whether they're mainly caused by estrogen or progesterone changes.

Changes in your menstruation

At first: shorter cycles, sometimes heavier bleeding
Later: longer cycles, skipped periods, often light bleeding

Important to know

During perimenopause, hormone replacement therapy is already possible, tailored to your symptoms (for example, cyclical progesterone and/or estrogen, always in consultation with your doctor)
Getting pregnant is still possible during this period — contraception therefore remains important

Your symptoms are real — and you're not alone in this.

This information is intended solely for educational and informational purposes. It does not replace medical advice, diagnosis, or treatment by a doctor or other qualified healthcare provider. Always consult your (family) doctor if you have questions or concerns about your health or treatment.