Irregular periods in your forties
Cycles that shorten, lengthen, disappear then return, or turn unexpectedly heavy. What is expected during the transition, what is not, and the specific bleeding patterns that always need checking.
Changing cycle length is usually the first objective sign of perimenopause. A persistent difference of seven days or more between consecutive cycles marks the early transition; a gap of 60 days or more marks the late transition. Irregularity is expected. Bleeding that is very heavy, lasts longer than seven days, occurs between periods or after sex, or happens at all after twelve months without a period, is not, and is always investigated.
What to hold on to
- Cycle change usually comes before hot flushes, not after them.
- The clinical staging system used by specialists is based on cycle variability: a persistent seven-day difference marks the early transition, a 60-day gap marks the late one.
- Heavier and closer together is a very common early pattern, and it is frequently mistaken for something being wrong.
- You can still conceive during perimenopause. Contraception is still relevant until twelve months after the last period, or two years if you are under 50.
- Any bleeding after twelve months without a period is investigated every time, regardless of how light it is.
What the change usually looks like
Rarely a smooth taper. More often: a run of cycles that arrive early, then one that is late, then two heavy ones, then nothing for six weeks, then a normal one that makes you wonder whether you imagined the whole thing.
Specialists stage the transition using exactly this variability. A persistent difference of seven days or more between consecutive cycle lengths marks the early transition. A gap of 60 days or more marks the late transition, which typically runs one to three years before the final period.
Why heavy bleeding happens
In a standard cycle, an egg is released and the corpus luteum produces progesterone, which stabilises the uterine lining and sets up an organised shed. In the transition, cycles where no egg is released become more frequent.
Oestrogen still builds the lining; the progesterone that would have organised its exit does not arrive. The lining gets thicker and comes away less tidily.
That is the mechanism behind the heavier, longer, less predictable bleeding many women describe in their early forties. It is common, and it is treatable.
It is also worth taking seriously, because sustained heavy bleeding is one of the more common causes of iron deficiency in women of this age and produces its own fatigue, breathlessness and palpitations.
The rules that never bend
Bleeding after twelve months without a period is investigated, every time, without exception, no matter how light it was or how long ago. Most causes turn out to be benign.
The reason the rule is absolute is that the one cause that is not benign is highly treatable when it is found early.
Bleeding between periods, bleeding after sex, and bleeding heavy enough to soak protection hourly all warrant assessment rather than management.
What else could cause this
Not everything in your forties is hormonal. These are the other explanations worth ruling out, and how they usually differ.
- Fibroids
- Very common in this age group, especially in Black women, and a leading cause of heavy prolonged bleeding. Usually diagnosed with an ultrasound scan.
- Endometrial polyps
- Cause bleeding between periods and after sex. Usually benign and usually straightforward to remove.
- Thyroid dysfunction
- Both overactive and underactive thyroid disturb cycles. A blood test settles it and it should be done.
- Pregnancy
- A missed period in your forties is not automatically the transition. Fertility falls but does not reach zero until it does.
- Endometrial hyperplasia or cancer
- Uncommon, and the reason the bleeding rules exist. Postmenopausal bleeding, bleeding between periods and persistent heavy bleeding are investigated precisely so that this is ruled out early, when it is highly treatable.
When to speak to a professional
- You are soaking through a pad or tampon every hour for several hours.
- Bleeding lasts longer than seven days, or you are passing clots larger than a ten pence coin or a quarter.
- You bleed between periods or after sex.
- You are tired, breathless or dizzy, which may indicate iron deficiency from blood loss.
Seek care urgently, not an appointment next month, if: any bleeding at all after twelve months without a period; soaking through protection hourly for several hours.
Is this one thing, or part of a pattern?
Most women arrive noticing one change and find four more they had filed under stress or a bad week.
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Is it normal for periods to get heavier?
It is common. In the early transition, cycles where no egg is released mean the uterine lining is exposed to oestrogen without the balancing effect of progesterone, so it builds up more and sheds more heavily. Common does not mean it has to be endured: heavy bleeding causes iron deficiency and there are effective treatments.
How do I know when I have actually reached menopause?
Menopause is diagnosed in retrospect, twelve consecutive months after your final period. There is no blood test that confirms it reliably during the transition, because hormone levels swing week to week. That is why symptom and cycle history matter more than a single result.
Can I still get pregnant?
Yes. Fertility declines but does not stop until the transition is complete. Standard guidance is to continue contraception for twelve months after the last period if you are over 50, and for two years if you are under 50.
Things that often come together with this
Sources
Updated 27 August 2026
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