Irregular Periods in Perimenopause: What's Normal, What's Not, and When to Worry

When Your Period Stops Making Sense

For years your period arrived on a schedule. Maybe it was not perfectly clockwork, but it was recognizable. Then, somewhere in your late 30s or 40s, things started shifting. Cycles that were 28 days became 24, then 35, then 45. A period that was light one month was flooding the next. Or your period simply did not show up for two or three months, then returned as if nothing had happened.

This is perimenopause. And the range of "normal" during this transition is so wide that almost anything your period does can be considered expected, with some important exceptions.

Understanding the full spectrum of perimenopausal menstrual changes, and knowing which patterns require evaluation, is one of the most practically useful things you can do for your health during this transition.

The Full Spectrum of Irregular: What Is Actually Normal

Perimenopause-related menstrual irregularity can look like many different things simultaneously or in sequence.

Cycles can become shorter, under 21 days, which often happens in early perimenopause due to a shortened follicular phase (the first half of the cycle). They can also become longer, over 35 days, as anovulatory cycles become more common. You may skip periods entirely for one, two, or even three months and then have them return. You may have two periods within a single month followed by a month with none.

Flow can change dramatically. Lighter periods are common, particularly with anovulatory cycles that produce a thin uterine lining. Heavier periods, including flooding (soaking through a pad or tampon in an hour or less), passing clots larger than a quarter, or bleeding that requires double protection, are also common and can occur unpredictably. The shift to heavier flow often comes before cycles lengthen or stop.

Anovulatory Cycles and Their Effects

An anovulatory cycle is one where your body goes through a cycle but does not release an egg. In perimenopause, anovulatory cycles become increasingly common. They can look very different from ovulatory cycles.

Without ovulation, there is no progesterone production from the corpus luteum. The uterine lining continues to grow under estrogen stimulation but does not receive the signal to stabilize and shed in an organized way. When bleeding finally occurs, it may be heavier and more prolonged than a normal period, or it may be unexpectedly light and brief.

Anovulatory cycles also mean no PMS in the classic sense, because PMS requires the progesterone rise and fall that only follows ovulation. Some people find relief from premenstrual symptoms during anovulatory stretches. Others find that the loss of progesterone entirely produces its own mood and anxiety effects, as described in the perimenopausal mood swings discussion.

When Irregular Bleeding Needs Evaluation

Not every irregular pattern is simply perimenopause. Certain patterns warrant prompt evaluation to rule out conditions including uterine polyps, fibroids, endometrial hyperplasia, or in rare cases endometrial cancer.

See your provider if you experience: bleeding between periods (not just variations in cycle timing), soaking through more than one pad or tampon per hour for two or more consecutive hours, periods lasting longer than seven days, any bleeding that occurs after a full year without periods (this is by definition postmenopausal bleeding and always warrants investigation), or spotting after sex.

Endometrial hyperplasia, where the uterine lining overgrows due to unopposed estrogen, is a particular risk in anovulatory perimenopause when estrogen remains present but progesterone is absent. The lining can overgrow without shedding, which eventually requires intervention. Heavy, prolonged, or irregular bleeding in perimenopause often prompts an endometrial biopsy or transvaginal ultrasound to evaluate the lining thickness. This is a routine and appropriate evaluation, not an alarming one.

Fibroids and Polyps in Perimenopause

Uterine fibroids are benign growths of uterine muscle that are extremely common (present in over 70% of people by menopause) and often become more symptomatic in perimenopause, when estrogen levels fluctuate at higher-than-normal levels before ultimately declining.

Fibroids can cause heavy and prolonged bleeding, pelvic pressure, increased urinary frequency, and painful periods. If you had fibroids in your 30s that were manageable, they may become more symptomatic in your 40s before they eventually shrink in postmenopause.

Endometrial polyps are overgrowths of the uterine lining and tend to cause irregular or spotty bleeding between periods as well as heavy periods. They are diagnosed by ultrasound or hysteroscopy and can be removed relatively easily. Both fibroids and polyps are benign but can significantly worsen the perimenopausal bleeding experience and should be evaluated if your bleeding pattern is severe or has features beyond typical perimenopausal irregularity.

Birth Control in Perimenopause

Many clinicians recommend ongoing contraception until full menopause (12 consecutive months without a period) because anovulatory cycles are interspersed with ovulatory ones, and pregnancy remains possible in perimenopause, including into the mid-40s and beyond.

The choice of contraception in perimenopause has additional dimensions beyond preventing pregnancy. Hormonal IUDs (Mirena, Liletta) deliver progestogen locally to the uterine lining and can dramatically reduce heavy perimenopausal bleeding while providing contraception. Many people find this one of the most effective ways to manage the flooding that characterizes perimenopausal heavy periods.

Combined oral contraceptives can also suppress perimenopausal symptoms and regulate bleeding, though they are not recommended in people over 35 who smoke or who have certain cardiovascular risk factors. Low-dose hormonal contraceptives differ from postmenopausal hormone therapy in their formulation and dosing. If you are using contraceptives and wonder how that interacts with your perimenopause, that is a specific conversation worth having with your provider.

Tracking for Your Own Sanity and Your Doctor

When Will This Stop?

One of the most common questions about perimenopausal irregular periods is simply: how long does this go on? The honest answer is that the timeline varies considerably. Perimenopause averages four to eight years, and menstrual irregularity is present for most of that time.

For most people, the sequence is: cycles first becoming shorter, then progressively more irregular and often heavier, then beginning to skip, then the gaps between periods extending to several months, and eventually to 12 consecutive months, which marks the formal end of perimenopause. The final year before menopause often brings the fewest and longest cycles.

Knowing this arc does not make the uncertainty easier, but it does make it finite. Irregular periods are not indefinite. The transition ends, and the physical experience of your period ends with it.

This content is for informational purposes only and does not replace medical advice. Always consult your healthcare provider about your specific situation.