In the UK, the average age of menopause is 51, but missing periods in the late 40s or early 50s are not automatically menopause. In UK primary care, the first job is to separate the expected cycle disruption of perimenopause from secondary amenorrhoea caused by pregnancy, endocrine disease, hypothalamic suppression, polycystic ovary syndrome or premature ovarian insufficiency. That distinction decides whether the woman needs symptom-led menopause care, contraception advice and possible HRT, or a broader work-up and referral.
Where the overlap starts
Perimenopause sits in the middle of this diagnostic trap. In NHS primary care, it is the stage before menopause, characterised by irregular menses and vasomotor symptoms, and menopause itself is defined as 12 months after the last menstrual period. British Menopause Society materials place the median age at 51 with a median menopause transition of 7.4 years. That means irregular or absent periods in a woman in her late 40s or early 50s may fit the hormonal transition, but the same pattern still overlaps with disorders that need treatment.
Secondary amenorrhoea is not a diagnosis in itself. NHS Scotland’s Right Decisions resource uses the absence of menses for 3 to 6 months in someone who previously had regular cycles, or 6 to 12 months in someone with prior oligomenorrhoea, as the threshold for secondary amenorrhoea. It occurs in 3 to 5% of women of reproductive age, and PCOS is the most common cause. A woman can be moving through perimenopause and still have a separate cause of amenorrhoea at the same time.
What should make GPs slow down before calling it menopause
The first question is whether the bleeding pattern is actually consistent with perimenopause or whether something else is driving it. A careful menstrual history should cover when the cycle changed, whether bleeding has become irregular rather than absent, and whether there are vasomotor symptoms such as hot flushes or night sweats. It should also check for pregnancy possibility, weight loss or gain, stress, exercise load, eating patterns and medication use, because all can suppress ovulation and interrupt periods.
That broader history is essential because secondary amenorrhoea can reflect reproductive, endocrine or lifestyle-related causes. Pregnancy and lactation remain physiological causes that should always be considered first. Other common differentials include thyroid disease, high prolactin levels, pituitary disorders, functional hypothalamic amenorrhoea linked to weight loss, heavy exercise or stress, PCOS and premature ovarian insufficiency. In women in their 40s and early 50s, sleep disturbance, low mood and fatigue can sit alongside cycle disruption, which makes it easy to overcall menopause when the actual problem is different.
What blood tests can and cannot do
The British Menopause Society’s guidance is blunt on routine testing in women over 45: blood tests are rarely required to diagnose perimenopause or menopause and should not be taken. The reason is FSH, which fluctuates significantly and bears no clear relation to symptom severity. A single FSH result does not solve the diagnostic problem when the clinical story already points to the menopause transition.
That does not mean testing has no place. It means the test strategy should match the presentation. When amenorrhoea is atypical, prolonged, or accompanied by clues to thyroid, prolactin, pituitary or ovarian pathology, the priority is to look for the underlying cause rather than to chase a menopause label. NICE’s *Menopause: identification and management* guideline, NG23, was first published on 12 November 2015, and the British Menopause Society dates the updated version to November 2024. The guideline backs a symptom-led approach rather than a lab-led one for typical midlife menopause care.
When the differential has to widen
The age of the patient changes the interpretation. A prolonged gap in periods in a woman in her 20s or 30s should not be assumed to be menopause. A Royal Australian College of General Practitioners case involved a 21-year-old with a 12-month history of amenorrhoea, a useful reminder that age should immediately shift the differential towards POI and other pathology. The British Menopause Society’s 2024 consensus statement on premature ovarian insufficiency treats POI as a separate possibility rather than folding it into a menopause assumption.
That same logic applies in primary care when a woman in midlife has missing periods but the pattern is not neatly perimenopausal. If she has marked weight loss, restrictive eating, heavy training, significant psychosocial stress, galactorrhoea, headache, visual symptoms, thyroid symptoms or a history that points to medication effects, the diagnostic frame should move away from “expected transition” and towards specific pathology. The practical error to avoid is over-reassurance, where a symptom is dismissed as menopause before pregnancy or endocrine disease has been checked.
What a good general-practice assessment looks like
A structured consultation does most of the work. Ask when the last period occurred, whether cycles had become progressively irregular before they stopped, and whether there are vasomotor symptoms that support perimenopause. Then check for features that point elsewhere: weight change, exercise patterns, eating behaviour, stress, medication changes, thyroid symptoms, galactorrhoea, headaches, visual disturbance, and any possibility of pregnancy.
In women who are clearly in the typical menopause age range and have classic symptoms, symptom-led treatment may be enough. In women whose amenorrhoea is prolonged, unexplained or discordant with the rest of the story, the threshold for investigation should be lower. One path leads to counselling, contraception and menopause management, while the other can uncover a condition that needs endocrine, reproductive or specialist assessment.
The practical takeaway for UK primary care
Perimenopause is common, and missing periods are often part of it. But secondary amenorrhoea is common enough, affecting 3 to 5% of women of reproductive age, that it should never be brushed off as a menopause default. The safest approach is simple: take the menstrual history seriously, consider pregnancy first, look for lifestyle and endocrine causes, and use FSH sparingly, if at all, in women over 45.