Summary: Menopause is defined in hindsight, after 12 months in a row without a period. Perimenopause is the transition before it, often lasting several years, when cycles become irregular and symptoms can begin. Postmenopause is everything after. For most people over 45, clinicians identify the stage from cycle history and symptoms rather than a single blood test.
What is perimenopause?
Perimenopause is the stretch of time when the ovaries’ hormone output becomes less predictable and menstrual cycles start to change. In the most widely used research framework, called STRAW+10 (the Stages of Reproductive Aging Workshop, updated in 2012), perimenopause begins with the early menopausal transition and ends 12 months after the final menstrual period (Harlow et al., 2012).
The framework describes two phases of the transition:
- Early transition (Stage −2): cycle length starts to vary, defined as a persistent difference of 7 days or more between consecutive cycles.
- Late transition (Stage −1): gaps between periods of 60 days or longer. STRAW+10 notes this phase lasts, on average, 1 to 3 years.
Symptoms can start during either phase. That is why many people notice night sweats, sleep changes, or shifting cycles well before anyone would call it “menopause.”
What counts as menopause?
Menopause itself is a single point in time: the final menstrual period. Because nobody knows a period is the last one when it happens, it can only be identified looking back, after 12 consecutive months without bleeding (Harlow et al., 2012). A 2018 review by Harlow, indexed in the CDC’s research library, uses the same definition for women aged 40 and older and notes that “another menstrual bleed may occur in up to 10% of women” (Harlow, 2018).
In the large US cohort study SWAN (the Study of Women’s Health Across the Nation), the median age at the final menstrual period among 3,302 participants was 52.54 years (Gold et al., 2013). That is a study median in one population, not a deadline; menopause at younger or older ages is common.
Postmenopause is the time after that final period. STRAW+10 splits it into early postmenopause (Stages +1a, +1b, and +1c, lasting roughly 5 to 8 years in total) and late postmenopause (Stage +2), which continues for the rest of life.
What is STRAW+10 staging?
STRAW+10 is a staging system researchers and clinicians use to describe where someone is in reproductive aging. It relies mainly on menstrual cycle patterns, with hormone levels and other markers as supporting criteria. In plain terms, the stages run like this:
- Stage −2, early menopausal transition: cycle length varies by 7+ days, persistently.
- Stage −1, late menopausal transition: 60+ days without a period; lasts about 1–3 years on average.
- Stage 0, final menstrual period: confirmed after 12 months with no period.
- Stages +1a and +1b, early postmenopause: together about 2 years; hot flashes most likely here.
- Stage +1c, early postmenopause: about 3–6 years; hormone levels stabilize.
- Stage +2, late postmenopause: the remaining lifespan.
Source for the stage list: Harlow et al., 2012 (STRAW+10), as summarized by ASRM.
STRAW+10 is a descriptive framework. It helps explain what is typical, but individual timelines vary a lot.
How long does perimenopause last?
It varies widely. In a SWAN analysis of 1,145 women, the adjusted median length of the menopausal transition (the main part of perimenopause, running from the first persistent cycle changes to the final period) ranged from about 8.6 years for women in the youngest quarter of starting ages to about 4.4 years for those in the oldest quarter (Paramsothy et al., 2017). Perimenopause as STRAW+10 defines it continues for 12 more months after that final period. The same analysis found that smoking was associated with an earlier start and a shorter transition. These are observational findings: they describe patterns in a study group and do not predict any one person’s timeline.
Symptoms can also outlast the transition. In another SWAN analysis of 1,449 women with frequent hot flashes or night sweats, the median total duration of those symptoms was 7.4 years, and they persisted a median of 4.5 years after the final period. Women whose symptoms began earliest, in premenopause or early perimenopause, had the longest duration, a median of more than 11.8 years (Avis et al., 2015).
Can a blood test tell which stage I’m in?
Usually not on its own. Hormone levels, including follicle-stimulating hormone (FSH) and estradiol, can swing widely from month to month during the transition, so a single result may not reflect where someone is.
That is why the UK’s National Institute for Health and Care Excellence (NICE) guideline NG23 advises that, for otherwise healthy people aged 45 and over with symptoms, clinicians identify perimenopause and menopause without laboratory tests. Under NG23:
- Perimenopause is identified from vasomotor symptoms (hot flashes and night sweats) plus changes in the menstrual cycle.
- Menopause is identified after at least 12 months without a period in someone not using hormonal contraception, or from symptoms in someone who has had their uterus removed.
- Clinicians are advised not to use tests such as anti-Müllerian hormone (AMH), inhibin A or B, estradiol, antral follicle count, or ovarian volume to diagnose menopause in people aged 45 and over.
- FSH should not be used to diagnose menopause in people taking combined estrogen and progestogen contraception or high-dose progestogen.
- An FSH test may be considered for people aged 40 to 45 with symptoms, or under 40 when menopause is suspected.
Guidelines in other countries differ in detail, so the right approach is something to talk through with a clinician who knows your history. This article is not a substitute for that conversation.
What about surgical menopause, early menopause, and POI?
The 12-month calendar rule does not fit everyone:
- Hysterectomy (uterus removed, ovaries kept): periods stop, but the ovaries keep working until their own natural transition. Because there is no period to count, NICE advises identifying menopause from symptoms instead.
- Hormonal contraception, including hormonal IUDs: these can lighten or stop periods, which hides the calendar signal. NG23’s 12-month definition applies only to people not using hormonal contraception, and it cautions against using FSH in people on combined contraception or high-dose progestogen.
- Surgical menopause: removing both ovaries ends ovarian hormone production at once, so menopause begins immediately rather than after a gradual transition. NICE advises that people likely to go through menopause because of surgery or medical treatment (such as some cancer treatments) receive information and support beforehand.
- Early menopause: NICE describes menopause between ages 40 and 44 as early menopause.
- Premature ovarian insufficiency (POI): menopause-like loss of ovarian function before age 40. NICE advises diagnosing POI from menopausal symptoms plus elevated FSH on two blood samples taken 4 to 6 weeks apart, not from a single test.
Early menopause and POI can carry different health considerations, so they are worth raising specifically with a clinician.
What symptoms show up in each stage?
Symptoms don’t follow a strict schedule, but research points to broad patterns:
- Perimenopause: changes in cycle length and flow are the defining feature. Hot flashes, night sweats, and sleep disruption often begin here; in SWAN, women whose hot flashes started earliest tended to have them longest (Avis et al., 2015).
- Early postmenopause: STRAW+10 notes vasomotor symptoms are most likely in the first couple of years after the final period (Stages +1a and +1b).
- Later postmenopause: vaginal and urinary changes related to lower estrogen, sometimes called genitourinary syndrome of menopause, tend to become more noticeable over time, as described in STRAW+10’s late postmenopause stage.
Many symptoms of perimenopause overlap with other conditions, such as thyroid problems. A new or worrying symptom is a reason to see a clinician rather than assume it is the transition.
FAQ
How do I know if I’m in perimenopause or menopause?
Menopause is confirmed only after 12 months in a row without a period. Before that, irregular cycles plus symptoms like hot flashes usually point to perimenopause. For people 45 and over, guidelines such as NICE NG23 advise clinicians to identify the stage from cycles and symptoms, not blood tests.
What is the average age of menopause?
In the SWAN study of 3,302 US women, the median age at the final menstrual period was 52.54 years (Gold et al., 2013). Individual ages vary widely.
How long does perimenopause last?
In SWAN, the adjusted median length of the menopausal transition, the main part of perimenopause, ranged from about 4.4 to 8.6 years depending on the age it began (Paramsothy et al., 2017). The late transition alone lasts about 1 to 3 years on average, per STRAW+10.
Can you get pregnant during perimenopause?
Pregnancy is still possible until menopause is confirmed, because ovulation can continue irregularly. Contraception questions are best discussed with a clinician.
Is there one blood test for menopause?
No single test reliably confirms it for most people over 45. NICE NG23 reserves FSH testing for specific situations, such as people aged 40 to 45 with symptoms or suspected menopause under 40.
Sources (all accessed Sep 28, 2026)
- Harlow SD, et al. Executive summary of the Stages of Reproductive Aging Workshop + 10 (STRAW+10), 2012. American Society for Reproductive Medicine: https://integration.asrm.org/practice-guidance/practice-committee-documents/executive-summary-of-the-stages-of-reproductive-aging-workshopd10-addressing-the-unfinished-agenda-of-staging-reproductive-aging-2012/
- National Institute for Health and Care Excellence. Menopause: identification and management (NG23), Recommendations: https://www.nice.org.uk/guidance/NG23/chapter/Recommendations
- Paramsothy P, et al. Duration of the menopausal transition is longer in women with young age at onset: the multiethnic Study of Women’s Health Across the Nation. Menopause. 2017. PMC5266650: https://pmc.ncbi.nlm.nih.gov/articles/PMC5266650/
- Gold EB, et al. Factors related to age at natural menopause: longitudinal analyses from SWAN. Am J Epidemiol. 2013. PMC3698989: https://pmc.ncbi.nlm.nih.gov/articles/PMC3698989/
- Avis NE, et al. Duration of menopausal vasomotor symptoms over the menopause transition. JAMA Intern Med. 2015. PMC4433164: https://pmc.ncbi.nlm.nih.gov/articles/PMC4433164/
- Harlow SD. Menstrual cycle changes as women approach the final menses: what matters? Obstet Gynecol Clin North Am. 2018;45(4):599–611. Indexed on CDC Stacks: https://stacks.cdc.gov/view/cdc/213402
This article is for general education and is not medical advice. Talk with a qualified clinician about your own symptoms and health history.
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