What Is Perimenopause and When Does It Start?

Medically reviewed by Meg LaFerriere, APRN · Regulate Rx, Lee’s Summit, MO

If your periods, sleep or moods started acting strangely somewhere in your 40s, you’re not imagining it. You may be in perimenopause, the long, uneven runway before menopause.

What happens in your body during perimenopause?

Through your reproductive years, estrogen and progesterone rise and fall in a fairly predictable monthly pattern. In perimenopause, that pattern gets noisy. You ovulate less reliably, so some cycles produce little progesterone, while estrogen can swing higher or lower than you’re used to.

It’s not a smooth decline. It’s more like a dimmer switch that someone keeps flicking. That unpredictability is why symptoms can show up for a few months, fade, and then come back.

Your brain and body feel these shifts in many places. Estrogen receptors sit in the brain, skin, bones, joints, blood vessels and bladder, which is why perimenopause can affect sleep, mood, temperature and even joint comfort at the same time.

When does perimenopause usually start?

Most women notice the first changes in their 40s. The average age of menopause in the US is about 51, and perimenopause usually starts several years before that. Some women notice subtle shifts in their late 30s.

Things that may move the timeline earlier include:

• Smoking
• A family history of early menopause
• Certain cancer treatments, such as chemotherapy or pelvic radiation
• Surgery that removes or affects the ovaries

If your periods stop or become very irregular before age 40, see a clinician. That isn’t typical perimenopause and deserves its own workup.

How long does perimenopause last?

On average, about four years, according to Mayo Clinic. For some women it’s a few months. For others it stretches close to ten years. There’s no reliable way to predict your own timeline in advance.

Researchers often split it into early and late stages. In early perimenopause, cycles start to vary by a week or more. In late perimenopause, you may skip periods for 60 days or longer.

Symptoms don’t always follow the stages neatly. Some women have their roughest stretch early, while others feel fine until periods start skipping. Tracking your cycle for a few months is the simplest way to see where you are.

Perimenopause vs. menopause: what’s the difference?

People use these words interchangeably, but they mean different things. Here’s a quick comparison.

Stage	What it means	Periods
Perimenopause	Hormones fluctuate as ovarian function winds down	Still happening, often irregular
Menopause	A single point in time: 12 months with no period	Stopped for one full year
Postmenopause	Every year after that point	None

So if you still get periods, even unpredictable ones, you’re not in menopause yet. That matters for things like contraception, because pregnancy is still possible.

What are the first signs of perimenopause?

Early signs are often subtle. Changes in cycle length, heavier or lighter periods, worse PMS, new trouble sleeping and mood shifts are common first clues. Hot flashes and night sweats often show up later, though not always.

Because many of these symptoms overlap with thyroid problems, anemia, stress and depression, it’s worth talking with a clinician rather than self-diagnosing. Our women’s hormone program starts with a full conversation about your history and symptoms, plus labs where they’re useful.

At Regulate Rx in Lee’s Summit, Meg LaFerriere, APRN, sees many women who were told they were “too young” for hormone changes. Your age is part of the picture, but your symptoms matter just as much.

Frequently asked questions

Can perimenopause start at 35?

It’s possible but less common. Most women start noticing changes in their 40s. If you’re in your mid-30s with new cycle changes, a clinician should also check for other causes, such as thyroid issues or pregnancy.

Do you still ovulate during perimenopause?

Yes, often, but less predictably. Some cycles release an egg and some don’t. That’s why pregnancy remains possible until you’ve reached menopause.

Is perimenopause a medical condition?

No. It’s a normal life stage, not a disease. But the symptoms can be disruptive, and they’re treatable, so you don’t have to just push through.

Sources: The Menopause Society; Mayo Clinic; Cleveland Clinic; STRAW+10 Reproductive Aging Staging System; NIH/MedlinePlus

This article is for general education and isn’t medical advice. Treatments aren’t right for everyone, and results vary. Our practitioner reviews your health history before any treatment.