Perimenopause: the transition
Perimenopause is the stretch of time during which ovarian function becomes erratic. It begins with noticeable changes in the menstrual cycle and ends twelve months after the final menstrual period. It commonly lasts several years, and the length varies widely between individuals.
The defining feature is variability, not decline. Cycles lengthen, shorten, skip, and return. Hormone levels fluctuate rather than falling smoothly, which is why a single blood test at a single moment is a poor way to establish where someone is in the transition. This is also why symptoms in perimenopause are often more erratic — and more confusing — than in postmenopause: the underlying signal itself is unstable.
The research staging system clinicians refer to is the Stages of Reproductive Aging Workshop criteria, updated as STRAW+10 in 2012, which divides the transition into early and late stages based on changes in cycle length and hormone measures. You are unlikely to be given a STRAW stage in a routine appointment, but it is the framework behind statements like "early perimenopause".
What is worth tracking in perimenopause
Because the whole diagnosis is symptom-based, cycle data carries real weight here — more than in any other stage. Cycle start dates, cycle length, and how heavy each bleed is, alongside symptoms. Variability itself is the finding; you cannot demonstrate variability without a run of consecutive cycles recorded.
Menopause: one day, identified in hindsight
Menopause is not a phase. It is the date of the final menstrual period, and it can only be confirmed retrospectively, once twelve consecutive months have passed with no bleeding and no other explanation. In the UK the average age is around 51; figures of 51 to 52 are commonly cited internationally.
Menopause before 45 is described as early menopause. Before 40, the relevant diagnosis is premature ovarian insufficiency, discussed below.
The retrospective definition has a practical consequence: for a year you cannot know which side of the line you are on. Keeping a bleeding record through that period is what allows the date to be established later, rather than estimated.
Postmenopause: after the line
Postmenopause covers all the years after that twelve-month mark. Vasomotor symptoms often continue well into it — in the SWAN cohort, hot flashes and night sweats persisted for a median of 4.5 years after the final menstrual period, with a median total duration of 7.4 years — so "postmenopausal" does not mean symptom-free.
Some symptoms behave differently over this period. Genitourinary symptoms — vaginal dryness, discomfort during sex, urinary urgency, recurrent urinary infections — are, unlike hot flashes, typically progressive rather than self-limiting, and they are treated as a distinct question from systemic therapy. The umbrella term used in the literature is genitourinary syndrome of menopause.
Any bleeding after twelve months without a period is postmenopausal bleeding and always warrants prompt medical assessment. That is not a symptom to log and monitor; it is one to have looked at.
Surgical menopause: no transition at all
Removal of both ovaries — bilateral oophorectomy, often performed alongside hysterectomy or as risk-reducing surgery — causes an immediate fall in ovarian hormone production. Symptoms typically begin within days, and are frequently reported as more abrupt and more intense than those of a natural transition, because there is no gradual adjustment period.
Two distinctions people commonly get tangled:
- Hysterectomy without removal of the ovaries does not cause immediate menopause. Periods stop, because the uterus is gone, but the ovaries continue to function. Menopause then happens later and — without periods to track — cannot be identified by the twelve-month rule at all. Symptoms become the only signal, which makes symptom records unusually important in this group.
- Removal of the uterus changes the progestogen question. Whether endometrial protection is needed depends on whether there is an endometrium to protect. This is a clinical decision, and it is one of the more consequential things to have recorded accurately in your own notes.
Because there is no transition to observe, tracking in surgical menopause is less about detecting a pattern of variability and more about establishing a clear before-and-after and monitoring the response to whatever therapy follows. A baseline recorded in the first weeks is disproportionately valuable, and very often nobody suggests taking one.
Premature ovarian insufficiency: a different diagnosis
POI is loss of ovarian function before the age of 40. It affects approximately 1% of women. It is not simply "menopause, earlier" — it is diagnosed differently, it has causes worth investigating, and its long-term considerations are distinct.
Diagnosis, per the European Society of Human Reproduction and Embryology guideline on POI, rests on menstrual disturbance — oligomenorrhoea or amenorrhoea — together with raised follicle-stimulating hormone on two separate measurements taken at least several weeks apart. Unlike diagnosis over 45, laboratory testing here is central rather than unnecessary. Investigation of underlying cause, including genetic and autoimmune causes, is part of standard assessment.
Two things make POI a materially different situation. First, ovarian function can fluctuate, and intermittent ovarian activity — including spontaneous pregnancy — is documented, so a POI diagnosis does not carry the same finality as postmenopause. Second, the exposure period is much longer: a person diagnosed at 30 faces decades without ovarian hormones, which is why guidance places weight on bone and cardiovascular considerations and on hormone therapy continued at least to the average age of natural menopause. All of that is a clinician conversation; the point here is that POI is its own diagnosis, not a footnote to menopause.
For tracking, the long horizon is the defining fact. A record that has to run for decades, across changes of provider and often across countries, needs to be portable and to belong to you.
The four side by side
| How it is defined | How it is identified | What tracking is for | |
|---|---|---|---|
| Perimenopause | The transition: from cycle changes until 12 months after the last period | Symptoms plus irregular cycles; no lab tests needed over 45 | Demonstrating variability; establishing a symptom baseline |
| Menopause / postmenopause | 12 consecutive months with no period, no other cause; average around 51 | Retrospectively, from the bleeding record | Tracking symptom trajectory and response to therapy over years |
| Surgical menopause | Abrupt loss of ovarian function after removal of both ovaries | From the surgical history — onset within days | A clear before-and-after; monitoring the response to therapy |
| Premature ovarian insufficiency | Loss of ovarian function before age 40; around 1% of women | Menstrual disturbance plus raised FSH on two separate tests | A portable long-horizon record across decades and providers |
Where gender-affirming HRT sits
Gender-affirming hormone therapy is not a menopause stage, and it does not belong in the table above. It appears here because the tracking overlap is substantial and largely unacknowledged: many of the same symptoms are monitored, the same delivery routes are used, adherence matters for the same reasons, and the same problem exists of carrying a coherent record between providers.
People on long-term estradiol or testosterone therapy — and people who have had gonadectomy — also encounter questions about what happens if therapy is interrupted. Those are clinical questions, and the frameworks are different: WPATH Standards of Care version 8 and the Endocrine Society clinical practice guideline, rather than menopause guidance. See tracking gender-affirming HRT.
Why the distinction is worth getting right
Three practical reasons. Diagnosis differs: over 45 you are diagnosed on symptoms, under 40 you need blood tests on two occasions — knowing which applies stops you either chasing an unnecessary test or accepting a symptom-only assessment when investigation is warranted. Duration differs: a perimenopausal record may need to run for years, a POI record for decades, a surgical-menopause record starts abruptly and needs a baseline immediately. The conversation differs: "my cycles have been irregular for two years and here is the pattern" and "both ovaries were removed in March and here is what changed" are different consultations that happen to share a vocabulary.
HRT AI treats all four as distinct situations rather than variations of one, which is why setup asks which applies. What gets tracked, and what the weekly summary looks for, follows from that answer.