Signs of perimenopause at 40: the first changes to look for

Name: Signs of perimenopause at 40: the first changes to look for
Creator: MenoWoman

The first signs of perimenopause at 40 are usually changes in your periods, such as shorter or more variable cycles, along with poorer sleep and mood changes. Perimenopause most often starts in the mid-40s, but it can begin in the late 30s.^1,2

Researched by the MenoWoman team. Edited by Marcela Sat. Updated 7 November 2026. We may earn from links.

See a doctor for very heavy bleeding (soaking a pad or tampon every 1 to 2 hours, or large clots), bleeding between periods or after sex, periods less than 21 days apart or bleeding that lasts over 7 days.^1,2 Talk to a doctor about irregular periods in your early 40s or younger, as they can signal early menopause or POI.⁷

Can perimenopause start at 40, or even at 35?

Yes. Cleveland Clinic says perimenopause can start anywhere from the mid-30s to the mid-50s. It most often begins in the mid-40s, about 8 to 10 years before the final period.¹ Mayo Clinic also says some women notice changes in their 30s.²

The average age of the final period is around 51 to 52.^3,4 So signs at 40 are early but not unusual. Your age at onset can be earlier if you smoke, have a family history of early menopause or have had certain treatments.² See the average age of menopause for more on timing.

Menopause before 40 is called premature menopause, or premature ovarian insufficiency (POI). Between 40 and 45 it is called early menopause.⁸ These need a doctor's assessment; see early menopause and POI.

First signs of perimenopause

Early signs are often subtle and easy to put down to stress. The most common are:

Cycle changes: periods that come earlier or later than usual, or heavier or lighter flow.¹ Researchers define the early transition as cycle length varying by 7 days or more, again and again.^6,2
Sleep: trouble sleeping, sometimes with night sweats.⁷
Mood: irritability, anxiety or low mood.²
Heat: occasional hot flashes, often around a period.⁷
Other: tiredness, forgetfulness, lower sex drive, headaches and weight gain.^4,1

Some women have no clear symptoms at all.⁷ For the full list, see the perimenopause hub.

What early hot flashes and period changes feel like

A hot flash is a sudden wave of heat, often with sweating, flushed skin and a fast heartbeat, sometimes followed by a chill.³ Most last a few minutes; the US National Institute on Aging gives a range of 30 seconds to 10 minutes.^3,4 At 40 they may be mild or only happen around your period.⁷

Period changes are often the first clue. Cycles may get a little shorter at first, then less predictable.⁶ Some women have heavier periods. Very heavy bleeding is common in perimenopause but should still be checked, because it can cause low iron and has other possible causes.^1,2

Night waking, feeling more irritable before a period, or a shorter fuse at work can all be early signs. They are easy to blame on busy midlife, so tracking helps.²

Who is more likely to start perimenopause early

Mayo Clinic lists several factors linked to an earlier start:²

smoking, which brings menopause 1 to 2 years earlier
a family history of early menopause
cancer treatment such as chemotherapy or pelvic radiation
a hysterectomy, or removal of one ovary
thyroid disease, rheumatoid arthritis and other autoimmune conditions

If any of these apply and you notice changes at 40 or younger, mention them to your doctor.

Why blood tests often do not help in your 40s

Perimenopause is mainly a clinical diagnosis. That means a doctor bases it on your age, symptoms and cycle pattern.¹

Hormone levels rise and fall from day to day, so one blood test can look normal even when you are in perimenopause.¹ NICE, the guideline body for England, says women over 45 can be diagnosed without tests. It suggests considering an FSH test only between 40 and 45, or under 40 if menopause is suspected.⁵ For women over 45, it advises against using AMH or estradiol to diagnose perimenopause.⁵

Home urine tests measure the same FSH hormone. Read are at-home menopause tests accurate? before relying on one.

What else to rule out

Tiredness, low mood and period changes have many causes. A doctor may suggest tests to rule out other conditions.¹

Pregnancy is one of them. Pregnancy is still possible in perimenopause, even when periods are irregular. If you do not want to become pregnant, keep using contraception until a doctor advises you it is safe to stop.^1,2 UK NHS guidance, which follows Faculty of Sexual and Reproductive Healthcare (FSRH) advice, suggests contraception until 2 years after the last period if you are 40 to 50, or 1 year if over 50. HRT is not a contraceptive.¹⁰

Hormonal contraception and some treatments for heavy periods can mask the signs of perimenopause, which makes diagnosis harder.⁵ Tell your doctor about any medicines you take.

What to do next

Keep a simple diary of your periods, sleep, mood and hot flashes for two or three months. It helps a doctor see the pattern. Symptom apps are listed under tests, apps and services.

If symptoms bother you, treatment is available at any age. Cleveland Clinic lists options that include hormone therapy, some antidepressants, birth control pills, a hormonal coil (such as Mirena) and vaginal creams.¹ Which suits you depends on your symptoms, health and whether you also need contraception. Options are rated in the table below; see the perimenopause guide for the full list. Changes to your sleep routine and stress may also help you cope, even if they do not stop hot flashes.

Common myths about perimenopause at 40:

Myth: 40 is too young for perimenopause. Fact: it can start from the mid-30s, though the mid-40s is more usual.¹
Myth: a normal blood test rules it out. Fact: hormone levels swing from day to day, so one result can look normal.¹
Myth: irregular periods mean you cannot get pregnant. Fact: pregnancy is still possible until menopause is confirmed.^1,10

Questions you may want to ask your doctor:

Could these symptoms be perimenopause, or something else such as a thyroid problem or low iron?
Do I need any tests at my age?
Which treatments would suit me, and do I still need contraception?
What changes in my periods should make me come back sooner?

Bring your diary, a list of medicines and supplements, and any family history of early menopause.

What it is used for: evidence rated

Option	Evidence	What the research shows
Hormone therapy (HRT)	Strong evidence	The most effective treatment for hot flashes and night sweats.⁹
Non-hormonal prescription medicines	Strong evidence	SSRIs, SNRIs, gabapentin and fezolinetant are recommended for hot flashes when hormones are not suitable.⁹
Cognitive behavioral therapy (CBT)	Strong evidence	Recommended for hot flashes, and suggested by NICE for low mood or anxiety linked to menopause.^9,5
Period and symptom diary	Some evidence	Rated some because guidelines base diagnosis on symptoms and cycle pattern, not tests, though diaries themselves are rarely studied.⁵
FSH blood test (age 40 to 45)	Weak evidence	May be considered in this age group, but levels swing, so one result can mislead.^5,1

Ratings explained: how we rate. Always talk to a doctor or pharmacist before starting a medicine or supplement.