Heavy, Erratic, Unpredictable: What's Normal and What Isn't

Perimenopausal bleeding is supposed to be irregular. That's the defining feature of the transition, not a complication of it.

The difficulty is that "irregular is normal" gets used to wave away things that genuinely need looking at. Women in this age group are told to expect chaos, and then spend three years bleeding heavily enough to be anaemic, because chaos was the forecast.

Both things are true. Most of it is expected. Some of it isn't, and the boundaries are knowable.

Why bleeding goes strange

Ovulation becomes intermittent long before periods stop. Progesterone is produced only after ovulation, and progesterone is what organises the lining and triggers a clean, timed shed.

In a cycle without ovulation, estrogen builds the lining with nothing to oppose it. It thickens, becomes unstable, and eventually breaks down in a disorganised way — which is precisely what heavy, prolonged, unpredictable bleeding is.

This also explains the timing. Early perimenopause tends toward heavier and more frequent bleeding. Later perimenopause tends toward gaps.

Structural causes become more common in this age group too, and often coexist. Fibroids and polyps are frequent in the forties, and either can turn a hormonally irregular cycle into a genuinely disruptive one.

What's expected

Cycles becoming shorter, then longer, then unpredictable. Skipped periods, sometimes several, followed by resumption. Flow changing character. A period arriving twice in one month. Worse premenstrual symptoms than you had at 30.

None of that requires investigation by itself.

What warrants a conversation

Bleeding after twelve consecutive period-free months. The one absolute rule. Postmenopausal bleeding always needs assessment. Most causes are benign, but it's the main presenting symptom of endometrial cancer, and endometrial cancer found early is highly treatable. Don't wait to see whether it recurs.

Bleeding heavy enough to change what you do. The practical definition of heavy menstrual bleeding in guidelines is bleeding that interferes with physical, emotional, social or material quality of life. Soaking through a pad or tampon hourly for several hours, passing clots larger than a 10p coin or a quarter, flooding through onto clothes or bedding, or planning your week around your period.

Periods lasting longer than seven days when they didn't used to.

Bleeding between periods, repeatedly.

Bleeding after sex. Common causes are benign — including the fragile tissue of genitourinary syndrome — but cervical causes need excluding.

Unscheduled bleeding on HRT. Some irregular bleeding in the first three to six months of starting or changing hormone therapy is expected. Bleeding that starts after a settled period, or that persists beyond the initial months, should be reported. NICE updated its advice on this in 2026 to align with cancer referral guidance.

Symptoms of anaemia: exhaustion beyond the ordinary, breathlessness on stairs, palpitations, unusual pallor, or craving ice. Heavy bleeding depletes iron, and low ferritin produces fatigue and fog that get routinely misattributed to hormones. It's a simple test.

What an assessment usually involves

Often nothing dramatic. A conversation about the pattern. Blood tests including full blood count and ferritin. Frequently a pelvic ultrasound to look for fibroids or polyps and measure the endometrial thickness. Sometimes a biopsy of the lining, which is done in clinic and takes minutes — uncomfortable rather than a procedure.

Guidance in both the UK and US supports endometrial assessment in women over 45 with abnormal uterine bleeding, so being offered a biopsy is standard practice rather than a signal that someone is worried.

Treatment exists

Heavy perimenopausal bleeding is treatable, and a surprising number of women don't know it.

The hormonal intrauterine system is first-line in UK guidance for heavy menstrual bleeding, substantially reduces or stops bleeding for most users, and doubles as contraception and as the progestogen component of HRT if you go on to take it. Tranexamic acid, taken only during bleeding, reduces blood loss significantly and is non-hormonal. Combined hormonal contraception can regulate cycles in suitable women. Surgical options exist where fibroids are the driver.

Anaemia should be treated on its own terms rather than waiting for the bleeding to resolve.

What to bring

Dates of your last several periods. A rough note of flow. Whether you're bleeding between periods or after sex. Whether you're exhausted in a way that's out of proportion.

"My periods are all over the place" is easy to absorb into the expected chaos. "I've bled for nine days out of the last fourteen, I'm changing protection hourly on the heaviest days, and I'm exhausted" is a different conversation, and gets a different response.

Sources

- National Institute for Health and Care Excellence. Heavy menstrual bleeding: assessment and management (NG88). - National Institute for Health and Care Excellence. Suspected cancer: recognition and referral (NG12). - National Institute for Health and Care Excellence. Menopause: identification and management (NG23), unscheduled bleeding on HRT. Updated 2026. - American College of Obstetricians and Gynecologists. Practice Bulletin: Diagnosis of Abnormal Uterine Bleeding in Reproductive-Aged Women. - Munro MG, Critchley HOD, Fraser IS. The FIGO systems for nomenclature and classification of causes of abnormal uterine bleeding. Fertility and Sterility. 2011;95(7):2204–2208.