Perimenopause basics

Perimenopause is the transition before menopause: the years when your ovaries make estrogen and progesterone less predictably, your periods become irregular and symptoms such as hot flashes, broken sleep and mood changes can begin. It most often starts in the mid-40s, with a median onset near 47 in US studies, and typically lasts 4 to 8 years. Menopause itself is a single date, confirmed after 12 months without a period; the average age in the US is about 51 to 52.

Where to start

Begin with what is perimenopause?, which covers the hormones, the symptoms and how it is diagnosed. If you suspect it has started, early signs of perimenopause and how to know you are in perimenopause give you a practical self-check. If you are unsure which stage you are in, perimenopause vs menopause explains the clinical definitions.

The basics at a glance

Question	Short answer	Read the guide
What is it?	The years before your final period, when hormones fluctuate and symptoms begin	What is perimenopause?
How is it different from menopause?	Perimenopause is a transition; menopause is one date, 12 months after the final period	Perimenopause vs menopause
When does it start?	Median onset about 47; most women begin between 45 and 55	When does perimenopause start?
What are the first signs?	Usually subtle cycle changes, then broken sleep, night sweats or mood shifts	Early signs of perimenopause
How do I know I am in it?	Your age, a changing cycle and new symptoms, not a single blood test	How to know you are in perimenopause
How long does it last?	Typically 4 to 8 years; longer for women who start earlier	How long does perimenopause last?
What happens to my hormones?	Estrogen swings rather than simply falling; progesterone drops as ovulation falters	Hormones in perimenopause
When is menopause?	About 51 to 52 on average; before 45 is early and before 40 is premature	Average age of menopause
Can it start in my 30s?	Possible but uncommon; other causes should be ruled out first	Perimenopause in your 30s
Can I still get pregnant?	Yes, until menopause is confirmed	Pregnancy in perimenopause

What is happening to your hormones

The change starts in the ovary. As follicles run low, AMH and inhibin B fall, and FSH rises to push the remaining follicles harder. Progesterone drops in cycles without ovulation, which become more common, and this is one reason sleep and mood often shift before periods change much. Estrogen does not decline in a straight line: in SWAN, average estradiol did not start to fall until about 2 years before the final period, with surges and dips along the way. That is why a single blood test is a snapshot, not a diagnosis.

Clinicians stage the transition by your periods. In early perimenopause, cycle length varies by 7 days or more from one cycle to the next. In late perimenopause, you go 60 days or longer without a period. The full list of symptoms shows what can come with each stage.

When to see a clinician

You do not have to wait for menopause to get help: hot flashes, sleep disruption, mood changes, heavy bleeding and vaginal symptoms all have effective treatments. See a clinician if symptoms are affecting your daily life, if your periods became irregular before 40 or stopped before 45, or if you bleed between periods, after sex or more heavily than usual. The symptom check helps you organize what you are noticing, getting care in the US explains who to see, and the directory lists clinicians near you.