First signs of perimenopause: the early changes to notice

The first signs of perimenopause can be subtle: shorter cycles, poor sleep, mood shifts, worse PMS or hot flashes, sometimes while periods are still regular.

By The Change Champions team · Updated 2026-10-01

Part of our guide: Perimenopause basics: what it is, stages and how long it lasts

Something feels slightly off, but you can't quite name it. Your period came a few days early again. You're waking at 4am for no clear reason. Your patience runs out faster than it used to, and the week before your period feels harder than it did. If you're in your late thirties or forties, you may be wondering whether these are the first signs of perimenopause.

This article covers the early changes many women notice, why symptoms can start while your periods are still regular, and which early signs are worth checking with your doctor in case something else is behind them.

The short answer: the first signs of perimenopause are often small changes in your period, such as shorter cycles or a heavier or lighter flow. Other early signs include trouble sleeping, mood changes, worse PMS and hot flashes. These can begin while your periods still seem regular. Because thyroid problems, anemia and pregnancy can cause similar changes, it's worth getting new symptoms checked.

The first signs of perimenopause to look out for

Perimenopause usually starts in your mid- to late 40s, according to the US Office on Women's Health, though changes can begin earlier. It rarely announces itself. For most women, it starts with a handful of small shifts that are easy to put down to stress or a busy life.

Changes to your cycle. The Menopause Society, a leading US professional organization, says cycles may at first be shorter than usual. The number of days you bleed can change, and your flow may be heavier or lighter. Later, cycle lengths can vary by a week or more. Our guide to irregular periods in perimenopause explains what's typical.

Sleep changes. The Office on Women's Health says changing hormone levels in perimenopause can cause problems sleeping. You may find it harder to fall asleep or stay asleep, or wake in the early hours and struggle to drop off again. Night sweats can play a part too.

Mood changes. Irritability, anxiety and low mood are common in perimenopause. You might feel more easily overwhelmed, tearful or short-tempered than usual. The Menopause Society notes that women appear to be particularly vulnerable to depression during the perimenopause years. There's more in perimenopause rage, tears and everything in between.

PMS-like changes. The Office on Women's Health says PMS symptoms may get worse in your late 30s or 40s as you approach menopause and during perimenopause. If the days before your period have started to feel noticeably harder, with more irritability, low mood or tiredness, this may be part of the picture.

Hot flashes. A sudden wave of heat through your face, neck or chest, sometimes followed by sweating or chills, is one of the best-known signs. The Menopause Society says hot flashes and night sweats are the most commonly reported symptoms of the transition.

Brain fog. Forty to sixty percent of midlife women report cognitive symptoms such as forgetfulness and trouble concentrating. Losing words or your train of thought can be an early and unsettling change.

Not everyone notices all of these, and some women notice very few. For the bigger picture, see what perimenopause is.

Can perimenopause start while your periods are still regular?

Yes. Many women expect perimenopause to begin with missed periods, but symptoms can come first.

The hormone changes behind perimenopause can begin well before your cycle obviously changes. Estrogen and progesterone levels can start to fluctuate while your periods still arrive on time. The Office on Women's Health says changing hormone levels can cause hot flashes and problems sleeping, and that irregular periods are among the symptoms you may notice as you get closer to menopause.

Research backs this up. In the Study of Women's Health Across the Nation (SWAN), a long-running US study, some women first reported frequent hot flashes or night sweats while they were still classed as premenopausal. That meant they'd had a period in the last three months and no change in how regular their cycles were over the past year. Those who started early in this way tended to have hot flashes for longer.

Regular periods don't rule out perimenopause. For many women, the first signs show up in their sleep, mood or temperature before their calendar.

Tracking can make early patterns easier to see. Noting your cycle alongside how you're sleeping and feeling can reveal links you'd otherwise miss.

Early signs that need checking for other causes

Perimenopause is common, but it isn't the only explanation for these changes. The Office on Women's Health says missing a few periods doesn't always mean you're in perimenopause, and advises checking with your doctor to rule out pregnancy or a health problem. These are the main ones to keep in mind.

Pregnancy. A late or missed period in your forties can still mean pregnancy. You can get pregnant during perimenopause, even if you've missed periods for a month or a few months. If there's any chance, take a pregnancy test. Our guide to pregnancy and contraception in perimenopause has more.

Thyroid problems. According to the Office on Women's Health, one in eight women will develop a thyroid problem in her lifetime, and thyroid symptoms are sometimes mistaken for menopause. An overactive thyroid can cause feeling hot when others don't, anxiety, irritability, trouble sleeping and fewer periods. An underactive thyroid can cause tiredness, weight gain and irregular periods. A simple blood test can check your thyroid.

Iron-deficiency anemia. Heavier or longer periods, which are common in perimenopause, can lead to low iron. The Office on Women's Health lists fatigue and weakness as very common symptoms, along with dizziness, headaches and shortness of breath. Anemia often develops slowly, so it's easy to mistake for perimenopause tiredness.

Depression. Low mood that lasts most days for weeks, loss of interest in things you usually enjoy, or feeling hopeless deserves proper attention, whatever the cause.

When to talk to a doctor

You don't have to wait until symptoms are severe. If early changes are affecting your sleep, work or relationships, or you'd simply like to know what's going on, that's a good reason to book an appointment.

See your doctor promptly for very heavy periods, bleeding between periods, periods that come very close together or last longer than a week, or any bleeding after 12 months without a period. The same goes for ongoing tiredness, a racing heart, unexplained weight changes or low mood.

If you have thoughts of harming yourself, call or text 988 (the Suicide & Crisis Lifeline). Call 911 in an emergency, such as chest pain, severe shortness of breath or bleeding so heavy that you feel faint.

Frequently asked questions

What age do the first signs of perimenopause usually appear?

Perimenopause usually starts in your mid- to late 40s, according to the Office on Women's Health. Some women notice changes earlier. The average age of menopause in the US is 52, and perimenopause lasts about four years on average before that.

What does a period look like in early perimenopause?

Often, cycles get a little shorter at first. You may bleed for more or fewer days than usual, and flow can be heavier or lighter. Later, the gap between periods tends to vary more and some periods may be skipped.

Can you have perimenopause symptoms with regular periods?

Yes. Hormone levels can begin to fluctuate before your cycle clearly changes. Hot flashes, sleep problems and mood changes can all appear while your periods still come on time.

Is it perimenopause or my thyroid?

It can be hard to tell, because the symptoms overlap. Both can affect your periods, sleep, mood, weight and how hot or cold you feel. A blood test can check your thyroid, so it's worth asking your doctor, especially if you have a racing heart, unexplained weight changes or feel very tired.

Your next step

For the next two or three months, jot down the first day of each period, how heavy it was, and a word or two about your sleep and mood. It takes a minute a day, and it turns vague worries into a clear pattern you can share with your doctor.

To bring your early signs together in one place, try our symptom check-in. You may also find our weekly email helpful: calm, practical information, once a week.

This article is general information, not personal medical advice. If you have symptoms that worry you, please speak to your doctor.

A missed or late period can also mean pregnancy, so take a pregnancy test if there's any chance, even in your mid-forties.

Sources

Written by The Change Champions team, an independent educational site. Not reviewed by a clinician. How we write and fact-check.