Irregular periods during perimenopause are one of the earliest and most common signs that hormonal transition has begun. For most women, the menstrual cycle has been reliably predictable for decades. When it suddenly becomes erratic, it is natural to feel confused, anxious, or unsure about what is happening.
Why perimenopause changes your periods
During perimenopause, the hormonal sequence that governs the menstrual cycle is disrupted. The ovaries become less responsive to FSH as the supply of healthy follicles diminishes. Oestrogen levels fluctuate rather than following a regular cyclical pattern. Ovulation becomes inconsistent and eventually stops. Progesterone production, which depends on ovulation, becomes erratic as a result.
What period changes are normal during perimenopause
| Change | Often perimenopause-related? | When to seek help |
|---|---|---|
| Shorter or longer cycles | Yes | If sudden, severe or worrying |
| Missed period | Yes | Take a pregnancy test if pregnancy is possible |
| Heavy bleeding/flooding | Can happen | GP assessment if soaking protection hourly or clots are large |
| Bleeding after sex | No | Book GP assessment |
| Bleeding after 12 months without periods | No | Prompt medical assessment |
Shorter cycles
One of the earliest signs of perimenopause is a shortening of the menstrual cycle. Cycles that were reliably 28 days may become 24 or 25 days, meaning periods arrive more frequently than before.
Longer cycles and missed periods
As perimenopause progresses, cycles often lengthen and periods may be missed. A skipped period should always prompt a pregnancy test in women not yet confirmed as postmenopausal, as pregnancy remains possible throughout perimenopause.
Variable cycle length
Cycles differing by seven or more days between months is one of the defining features of early perimenopause, driven by the erratic hormonal fluctuation that characterises the transition.
Heavier periods and flooding
When ovulation does not occur or is delayed, progesterone is not produced. Without progesterone to stabilise the uterine lining, it continues to build under unopposed oestrogen, producing heavier and sometimes prolonged bleeding. Flooding and large clots should be assessed by a GP.
Lighter periods and spotting
Some women notice lighter periods as ovulation becomes less reliable. Spotting between periods can happen during perimenopause, but new, persistent, or unexplained bleeding between periods should still be discussed with a GP.
Important: bleeding after sex, very heavy bleeding, bleeding with large clots, or any bleeding more than 12 months after your last period should be discussed with a GP promptly. Postmenopausal bleeding can need urgent referral.
What is not normal: symptoms that need medical assessment
Postmenopausal bleeding
Postmenopausal bleeding, any bleeding that occurs more than 12 months after the last period, is always abnormal and requires prompt medical assessment. Report to your GP promptly. NICE guidance on suspected cancer specifies urgent referral for investigation.
Very heavy bleeding
Bleeding that soaks through a pad or tampon every hour for two or more consecutive hours, or includes clots larger than a 50p coin, warrants GP assessment to rule out fibroids, polyps, and other treatable conditions.
Bleeding after sex
Post-coital bleeding is not a normal feature of perimenopause and should be assessed to rule out cervical or vaginal conditions.
Contraception during perimenopause
Perimenopause is not infertility. Pregnancy remains possible until 12 consecutive months without periods confirm menopause. FSRH guidelines recommend contraception for two years after the last period for women under 50, and one year for women over 50. HRT is not a contraceptive.
Managing problematic perimenopausal bleeding
The Mirena hormonal IUS is one of the most effective treatments for heavy perimenopausal bleeding, significantly reducing or stopping periods while providing contraception and serving as the progestogen component of HRT when combined with systemic oestrogen. Sequential HRT, tranexamic acid, NSAIDs, combined hormonal contraception, and cyclical progestogen are all effective alternatives.
For related guidance, see am I in perimenopause?, perimenopause symptoms, and menopause blood tests.
Frequently Asked Questions
Why have my periods become irregular during perimenopause?
Irregular periods are caused by the declining and erratic production of oestrogen and progesterone as the ovaries transition towards menopause. Ovulation becomes inconsistent and eventually stops. Without the regular hormonal sequence that governs a normal cycle, periods arrive earlier, later, heavier, lighter, or not at all.
Is it normal to miss a period during perimenopause?
Yes. Missed periods are a normal feature of perimenopause, particularly as the transition progresses. However, a missed period in a woman who is still potentially fertile should prompt a pregnancy test, as pregnancy remains possible throughout perimenopause.
How heavy is too heavy during perimenopause?
Bleeding that soaks through a pad or tampon every hour for two or more consecutive hours, or includes clots larger than a 50p coin, should be assessed by your GP.
What is the difference between perimenopausal bleeding and postmenopausal bleeding?
Perimenopausal bleeding refers to any bleeding before 12 consecutive months without periods have passed. Postmenopausal bleeding is any bleeding after that 12-month point. It is always abnormal and should be assessed promptly, with urgent referral where indicated.
Do I still need contraception during perimenopause?
Yes. Pregnancy remains possible throughout perimenopause until 12 consecutive months without a period confirm menopause. UK guidelines recommend women under 50 continue contraception for two years after their last period, and women over 50 for one year. HRT is not a contraceptive.
What is the best treatment for heavy perimenopausal periods?
The Mirena hormonal IUS is one of the most effective treatments for heavy perimenopausal bleeding, significantly reducing or stopping periods while also providing contraception and optionally the progestogen component of HRT.
Can HRT regulate irregular perimenopausal periods?
Sequential HRT, which provides oestrogen daily and progesterone for 12 to 14 days of each cycle, typically produces a predictable monthly withdrawal bleed, making perimenopausal bleeding significantly more regular and manageable.
When should I see a doctor about my periods during perimenopause?
See your GP if you experience postmenopausal bleeding (always urgent), bleeding after sex, very heavy bleeding soaking through protection every hour, bleeding with large clots, or bleeding lasting longer than seven to ten days.
Author: The Menopause Directory
About this guide
This guide is published by The Menopause Directory editorial team to help UK readers understand menopause symptoms, support options and services. It is for general information only and should not replace advice from a GP, pharmacist or qualified menopause specialist.
Last reviewed by The Menopause Directory editorial team.