Heavy or irregular periods in perimenopause: what's normal and when to get checked

What changes in perimenopause

A typical menstrual cycle runs 24 to 38 days, and a normal period lasts up to 8 days, according to the American College of Obstetricians and Gynecologists (ACOG).¹ In your 40s that can shift. ACOG says periods may get shorter or longer, the days between them may grow or shrink, bleeding may get heavier or lighter, and you may skip periods.¹

Researchers who stage the menopause transition use cycle length as the marker. The early transition starts when your cycle length keeps changing by 7 days or more from one cycle to the next. The late transition starts when you go 60 days or longer without a period, and it lasts 1 to 3 years on average.⁵ Menopause is 12 months with no period, and the average age of the last period in the US is 51.¹ Our guide to the signs and stages of perimenopause covers the bigger picture.

Why periods can get heavier

When you don't ovulate regularly, parts of the uterine lining can get too thick. ACOG says this is common in perimenopause, and it can lead to heavy bleeding.²

How common long or heavy periods are

Some of the best numbers come from the Study of Women's Health Across the Nation (SWAN), which its authors describe as the only multi-ethnic study of bleeding patterns through the transition.⁴ In SWAN, 1,320 women in Michigan and California kept daily menstrual calendars between 1996 and 2006. They were African American, white, Chinese and Japanese women.⁴ Over about 10 years of follow-up⁴:

91% had at least one period that lasted 10 days or more, and 77.7% had three or more.
66.8% had three or more stretches of spotting that lasted 6 days or more.
34.5% had three or more periods with 3 or more days of heavy bleeding.

All three patterns were more common during the transition than before it, a little more so in the late stage. Long periods and long spotting were also more common in women with fibroids.⁴

Common doesn't mean you should ignore it. The SWAN researchers wrote that their data can't set a cutoff for when bleeding needs to be checked.⁴ ACOG still says to bring bleeding changes up with your ob-gyn.¹

What counts as heavy

ACOG lists these signs of heavy menstrual bleeding²:

Bleeding that lasts more than 7 days
Soaking through one or more tampons or pads every hour for several hours in a row
Needing to wear more than one pad at a time
Needing to change pads or tampons during the night
Passing clots as big as a quarter or larger

One small mismatch: ACOG's perimenopause page says a normal period lasts up to 8 days,¹ while its heavy-bleeding page counts more than 7 days as a sign.² Either way, a period that runs past a week is worth mentioning.

The UK's National Institute for Health and Care Excellence (NICE) defines heavy menstrual bleeding by what it does to your life: blood loss that "interferes with a woman's physical, social, emotional and/or material quality of life".³ NICE tells clinicians that treatment should aim to improve your quality of life, not just reduce blood loss.³ And if a woman feels her bleeding falls outside the normal range, NICE tells clinicians to discuss care options with her.³

You wouldn't be alone in asking. ACOG says about one in three women seek treatment for heavy bleeding.² In the UK, about 1 in 20 women aged 30 to 49 see their GP each year for heavy periods or menstrual problems.³

When to get checked

ACOG says these are not normal¹:

Bleeding or spotting between periods
Bleeding or spotting after intimacy
Heavy bleeding during your period
Bleeding that is heavier or lasts more days than usual
Bleeding after menopause

ACOG also notes that heavy periods can lead to iron-deficiency anemia, and that severe anemia can cause shortness of breath and raise the risk of heart problems.² NICE adds pelvic pain or pressure to the symptoms clinicians should ask about alongside heavy bleeding.³

Bleeding after menopause. Once you've gone 12 months without a period, any bleeding counts, including spotting. ACOG says it's especially important to tell your ob-gyn about it.¹ Bleeding is the most common sign of endometrial cancer after menopause, and most cases found early can be treated successfully.¹

What can cause abnormal bleeding

ACOG names several causes¹²:

Fibroids, polyps and adenomyosis. ACOG lists all three as causes of heavy bleeding. Polyps are noncancerous growths in the uterus that can cause irregular or heavy bleeding.
Irregular ovulation. Common in perimenopause, and also linked to polycystic ovary syndrome (PCOS) and an underactive thyroid.
Endometrial hyperplasia. A lining that gets too thick, most often from too much estrogen and not enough progesterone. It isn't cancer, but in some cases it can lead to cancer, and early treatment may lower that risk.
Bleeding disorders and some medicines, including blood thinners and aspirin, and the copper IUD.
Endometrial cancer. Less common. Heavy bleeding can be an early sign, and most cases are diagnosed in women in their mid-60s, after menopause, often at an early stage.

ACOG's list of risk factors for endometrial cancer includes getting older, irregular periods, obesity, PCOS, diabetes, high blood pressure, smoking, and treatment with tamoxifen, among others.¹

What a visit may involve

ACOG says your ob-gyn may ask about past and present illnesses and surgeries, your pregnancy history, your birth control, any medicines you take (including over-the-counter ones), and the details of several cycles.² You may have a pelvic exam, a pregnancy test and tests for some infections. Depending on your symptoms and age, you may also have an ultrasound, a hysteroscopy (a thin scope that looks inside the uterus), an endometrial biopsy (a small sample of the lining) or another imaging test.²

NICE recommends a full blood count for everyone with heavy bleeding.³ It recommends against female hormone blood tests for heavy bleeding, and against thyroid tests unless there are other signs of thyroid disease.³

What the options look like

ACOG says treatment depends on the cause,¹ and medicines are often tried first.² Here's what the sources describe:

Hormonal birth control. Depending on the type, ACOG says it can lighten flow, make periods more regular or stop bleeding.²
Hormone therapy. ACOG says it can help heavy bleeding in perimenopause, and that you should weigh the benefits against the risks, which include a higher risk of heart attack, stroke and cancer.²
A hormonal IUD. For heavy bleeding with no other cause found, small fibroids or adenomyosis, NICE says to consider a levonorgestrel-releasing IUD first. Bleeding often changes in the first few cycles, and NICE advises waiting at least 6 cycles to judge whether it's working.³
Other medicines. If a hormonal IUD isn't right for you, NICE lists both hormonal and non-hormonal medicines.³
Procedures, such as endometrial ablation, fibroid procedures or hysterectomy, when medicines don't help.² ACOG says ablation should be considered only after other treatments haven't worked, and that you'll need birth control until after menopause because pregnancy after ablation is unlikely but risky.²

NICE says your clinician should talk through all the options with you, including their benefits and risks and whether you want to keep your uterus.³ In NICE's words, "it is the woman herself who decides whether a treatment has been successful".³ Talk with your clinician about which options fit you.

What we don't know

SWAN didn't enroll women who had gone three months without a period, so it misses the very end of the transition, and fibroids were self-reported.⁴ It also can't say which bleeding patterns point to a problem.⁴ NICE is a UK guideline focused on women before menopause.³ ACOG's perimenopause bleeding page was last updated in 2020 and reviewed in 2024.¹

One thing to try

Track your bleeding before your appointment. ACOG suggests a calendar or app that records the date each period starts, how long it lasts, and the flow: light, medium, heavy or spotting.² Our two-week symptom tracker has a period row, and a simple calendar works for the months in between.

A question to bring

"My periods have changed. Is this pattern expected for where I am in perimenopause, or should we look for a cause? And should I have a blood count to check for anemia?"

If you'd like someone who knows this stage well, Talk to a menopause-trained provider.

Sources

American College of Obstetricians and Gynecologists. Perimenopausal Bleeding and Bleeding After Menopause (FAQ). Last updated October 2020, last reviewed February 2024. https://www.acog.org/womens-health/faqs/perimenopausal-bleeding-and-bleeding-after-menopause
American College of Obstetricians and Gynecologists. Heavy Menstrual Bleeding (FAQ). Last updated May 2021, last reviewed May 2026. https://www.acog.org/womens-health/faqs/heavy-menstrual-bleeding
National Institute for Health and Care Excellence. Heavy menstrual bleeding: assessment and management (NG88). Published March 2018, last updated July 2026. https://www.nice.org.uk/guidance/ng88
Paramsothy P, Harlow SD, Greendale GA, et al. Bleeding patterns during the menopausal transition in the multi-ethnic Study of Women's Health Across the Nation (SWAN): a prospective cohort study. BJOG. 2014;121(12):1564-1573. PMID: 24735184. https://pubmed.ncbi.nlm.nih.gov/24735184/
Harlow SD, Gass M, Hall JE, et al. Executive summary of the Stages of Reproductive Aging Workshop + 10: addressing the unfinished agenda of staging reproductive aging. Fertil Steril. 2012;97(4):843-851. PMID: 22341880. https://pubmed.ncbi.nlm.nih.gov/22341880/

Information for better conversations, not a diagnosis. We’re not clinicians; we read the research and show our sources. See our disclaimer.