When does perimenopause start?

What perimenopause is and when it starts

Perimenopause is the run-up to menopause: the years in which the ovaries make less estrogen, release an egg some months and not others, and your periods start to change. The American College of Obstetricians and Gynecologists (ACOG) says it typically begins in the mid-40s. Its patient guide on the menopause years places the first hormone fluctuations in the 30s and 40s.

Cleveland Clinic puts the possible start anywhere from the mid-30s to the mid-50s and says it usually begins eight to ten years before menopause itself. So a woman who reaches her last period at 51 may have had her first cycle changes at 43, and a woman whose periods stop at 55 may not notice anything until her late 40s.

There is no single day it begins. The first sign, for most women, is a change in periods. The NHS describes it as periods coming more or less often, or getting heavier or lighter. Hot flashes, sleep problems, mood changes and brain fog may arrive at the same time, later, or hardly at all.

Perimenopause age: what is typical, and what counts as early

The age of menopause frames everything else, because perimenopause is counted back from it. MedlinePlus, the US National Library of Medicine's health site, gives 45 to 55 as the most common age for menopause, and ACOG gives 51 as the average in the United States. Perimenopause in your early to mid-40s is therefore the expected timing.

Two cut-offs come up in every guideline:

• Early menopause is periods stopping before 45.
• Premature menopause is periods stopping before 40.

Those ages refer to menopause itself, and not to the first symptom. Noticing cycle changes at 41 does not mean you are heading for early menopause. Plenty of women spend most of their 40s in the transition and still reach their last period around 50.

Perimenopause vs premenopause vs menopause

The words get mixed up in articles and in conversation, so it helps to pin them down. Researchers use the STRAW+10 staging system, which divides adult life into three phases: the reproductive years, the menopausal transition, and postmenopause. In everyday terms:

• Premenopause is an everyday word, and it has no stage of its own in STRAW+10. Most people use it for the reproductive years before any change, and some use it loosely to mean perimenopause, which is where the confusion starts.
• Perimenopause is the stretch of years when cycles and hormones are changing, up to the last period and the year that follows it.
• Menopause is one point in time: the day you reach 12 months without a period. You only know the date afterwards, looking back.
• Postmenopause starts at that point and runs for the rest of your life, and some symptoms carry on into it.

When a friend says she is "in menopause" at 46 with periods still coming every few weeks, she almost certainly means perimenopause. The difference matters in practice: in perimenopause you can still ovulate and get pregnant, and bleeding is still expected. After menopause, any bleeding at all is a reason to see a doctor.

The stages, in the order they usually come

STRAW+10 is built on periods because they are the one marker anyone can record without a blood test. In the order the stages usually arrive:

1. Late reproductive years. Cycles are still regular, but subtle changes begin, specifically shorter cycles. Periods arriving every 24 days instead of every 28 is a common early hint.
2. Early transition. The length of one cycle differs from the next by 7 days or more, and that swing happens again within 10 cycles.
3. Late transition. A gap of 60 days or more with no period. STRAW+10 estimates this stage lasts 1 to 3 years on average, and it is when hot flashes and night sweats are most likely to show up.
4. The final period, recognised only once 12 months have passed without another one.

Not everyone moves through these neatly. Our guide to irregular periods in perimenopause goes through each cycle change and which ones to report, and heavy periods and blood clots in perimenopause covers the flooding that can come with longer cycles.

How long does perimenopause last?

Two different numbers get quoted, and both are right, because they measure different things.

The transition itself, from the first cycle changes to the last period, averages about four years according to Cleveland Clinic, and can run to eight. Some women pass through it in a few months.

Symptoms tend to outlast it. The NHS says menopause and perimenopause symptoms usually last 7 to 9 years, sometimes longer, and that they can change over time. Hot flashes that start in the late transition can carry on for years after menopause, while the cycle changes stop when periods do. That is why "how long does perimenopause last" and "how long will I feel like this" can have different answers for the same woman.

No test or app can tell you in advance how long yours will be. What you can know is roughly where you are, from the pattern of your cycles over the last year.

Early menopause age: before 45, and before 40

The NHS page on early or premature menopause says the main symptom is periods becoming irregular or stopping before 45. The other symptoms are the familiar ones: hot flushes and night sweats, vaginal dryness, trouble sleeping, low mood or anxiety, lower sex drive, and problems with memory or concentration.

The NHS lists what makes it more likely: early or premature menopause running in your family, starting your periods early, smoking, and being underweight. It can also follow medical treatment, such as radiotherapy or chemotherapy, certain hormone medicines, or surgery to remove the ovaries. Cleveland Clinic adds that people who smoke regularly tend to reach menopause one to two years earlier than those who do not.

The NHS says menopause before 45 brings a higher chance of osteoporosis and heart disease, so if your periods have become irregular or stopped in your early 40s or before, see a GP rather than waiting it out. Under 45, a GP may sometimes do blood tests.

Can a blood test tell you when it started?

Usually not, and over 45 a doctor will normally not try. The NICE guideline on menopause says perimenopause in women over 45 is identified from symptoms and any change in periods, without lab tests, and advises against using hormone tests such as AMH or estradiol for this. Hormone levels rise and fall so much in these years that one result says little. NICE reserves an FSH test for women aged 40 to 45 with symptoms, and for women under 40 when premature menopause is suspected.

So for most readers, the answer to "when did mine start?" comes from your own record of your cycles. Our overview of perimenopause symptoms and how to track them lists what to note beyond periods, and the printable symptom diary and appointment checklist gives you the rows to fill in.

What can hide the start

Some situations take away the signal most women rely on. The NHS points out that hormonal contraception, including the progestogen-only pill, the hormonal coil, the implant and the injection, can mask perimenopause, because it changes or stops your bleeding. If you have had a hysterectomy, there are no periods to watch at all. In both cases the other symptoms, and when they began, become the record that counts.

Starting perimenopause does not mean you can stop contraception. Ovulation carries on, irregularly, right up to the last period. The NHS advises using contraception until 2 years after your last period if you are 40 to 49, and for 1 year after it if you are 50 or over. A missed period in your 40s is worth a pregnancy test before you put it down to perimenopause.

My take

If you are 42 or 45 and your cycles have shortened or started to swing by a week, I would assume the transition has begun and start writing down period start dates now. That one list answers most of what a doctor asks. If your periods have become irregular or stopped before 45, book an appointment instead of waiting, for the bone and heart reasons the NHS gives. And I would not pay for a home hormone test to find out where you are: past 45, NICE does not use them, and before 45 it is your GP who decides which test is worth doing.

Related reading

The stages and timing topic collects every piece on when the changes come and how long they run, and spotting between periods in perimenopause covers the bleeding that should not wait for a routine appointment.