Heavy and Irregular Periods in Perimenopause: What's Normal, What's Not, and What Helps

For years your period was predictable. Now it shows up after 19 days, or 60. Some months it's light. Others, you're bleeding through a pad in an hour, planning meetings around the nearest bathroom, and wondering if something is seriously wrong.

Period changes are often the first clear sign of perimenopause, well before hot flashes. One search analysis found about 40% more interest in perimenopause searches about periods than in similar menopause searches, and for good reason: they're disruptive, and almost no one explains them.

Here's what's happening, what's normal, what isn't, and what you can do about it.

Why your period changes in perimenopause

In your 20s and 30s, you ovulate almost every month. After ovulation, the follicle that released the egg makes progesterone. Progesterone stabilizes the uterine lining so it sheds in an orderly way.

In perimenopause, ovulation becomes unreliable. Some cycles you ovulate, some you don't. When you don't, you make little or no progesterone that month. (For everything else progesterone does, see What Does Progesterone Do?)

Estrogen, meanwhile, doesn't simply fall. In early perimenopause it often swings high, sometimes higher than it was in your 30s. Estrogen builds the uterine lining. Without enough progesterone to balance it, the lining can grow thicker than usual and shed unpredictably. That's the classic setup for:

• Heavier periods, because there's more lining to shed
• Longer periods, because it doesn't shed cleanly
• Shorter cycles early on. Cycles under 21 days are common in early perimenopause, and both short and long cycles are more likely to be cycles without ovulation.
• Longer gaps later on. As you get closer to your final period, cycles stretch out, sometimes to 60 days or more.

This is why heavy bleeding is so often a perimenopause problem rather than a menopause problem. It's driven by too little progesterone relative to estrogen, not by low estrogen.

What's "normal" in perimenopause

The best data on this comes from SWAN, which had 1,320 women aged 42 to 52 keep daily menstrual calendars for up to 10 years. Over the transition, many women had at least three episodes of:

• Periods lasting 10 days or more: about 78% of women
• Spotting for 6 days or more: about 67%
• Heavy bleeding for 3 days or more: about 35%

So long, heavy, and irregular periods are common. That's reassuring, but it doesn't mean they're harmless or that you just have to put up with them.

A 2025 SWAN analysis of 2,329 women found that women with three or more episodes of heavy bleeding in six months were 1.62 times more likely to feel tired and 1.44 times more likely to feel worn out. Heavy bleeding has real effects on how you feel and function.

What counts as heavy?

Clinically, heavy bleeding means losing more than about 80 mL per cycle, but nobody measures that at home. Practical signs include:

• Soaking through a pad or tampon every hour or two
• Needing to double up on protection or change overnight
• Passing clots larger than a quarter
• Bleeding that limits work, exercise, or social plans

When to see a doctor

Common doesn't mean you should skip an evaluation. Get checked if you have:

• Bleeding between periods or after sex
• Periods closer than 21 days apart, or lasting more than 8 to 10 days, especially if repeated
• Heavy bleeding that soaks through protection hourly, or comes with dizziness, shortness of breath, or a racing heart
• Any bleeding after you've gone 12 months without a period
• A big change from your usual pattern that doesn't settle

Why age 45 matters

When estrogen runs unopposed by progesterone for long stretches, the uterine lining can overgrow. This is called endometrial hyperplasia, and in some cases it can progress to endometrial cancer.

Endometrial cancer is uncommon before 45, and most perimenopausal women with irregular bleeding don't have it. But because it's possible, the American College of Obstetricians and Gynecologists recommends sampling the uterine lining (an endometrial biopsy) for women over 45 with abnormal bleeding. It's also recommended for younger women with long exposure to unopposed estrogen, persistent bleeding, or bleeding that doesn't respond to treatment.

Fibroids and polyps are also common causes of heavy bleeding in the 40s. A biopsy can miss them, so an ultrasound is often part of the workup too.

The hidden cost: low iron

Heavy periods are the leading cause of iron deficiency in women who still menstruate. And iron deficiency causes many of the same symptoms women blame on perimenopause: fatigue, brain fog, low mood, hair shedding, restless legs, and feeling winded on the stairs.

The problem is that iron can be low long before you're anemic. Your hemoglobin can look normal while your iron stores, measured by ferritin, are nearly empty.

Many labs only flag ferritin below 15. Researchers increasingly argue for a cutoff of 30, because levels between 15 and 29 already reflect depleted stores. In a Monash University study of 736 Australian women with an average age of 32, about 35% had a ferritin below 30, and heavy menstrual bleeding was one of the strongest predictors.

If your periods are heavy, ask for a ferritin level, not just a complete blood count. And if your ferritin is low, find out why rather than just taking iron. The bleeding needs attention too. For which supplements are worth taking and which aren't, see Perimenopause Supplements: What Actually Works.

Treatment options

Once cancer, fibroids, polyps, thyroid problems, and bleeding disorders are ruled out, there are good options to discuss with your clinician. What fits depends on how heavy the bleeding is, whether you need contraception, and your other symptoms.

• Hormonal IUD (52 mg levonorgestrel). This has the strongest evidence. Across randomized trials, it cut blood loss by about 82%, compared with 26% for other medical treatments, and more women stayed on it at two years. It releases progestin directly into the uterus, which also protects the lining.
• Cyclic or daily progesterone. Because the root problem is often too little progesterone, adding it back in the second half of the cycle can help regulate bleeding. Micronized progesterone may also help sleep and night sweats.
• Tranexamic acid. A non-hormonal medication taken only on heavy days. It reduces blood loss in roughly 40% of women. It's less effective than the hormonal IUD and isn't right for women with a history of blood clots.
• Anti-inflammatory medications such as ibuprofen or mefenamic acid, taken during the period, can modestly reduce flow and cramps.
• Procedures such as endometrial ablation or hysterectomy, usually for bleeding that doesn't respond to other treatment, or for fibroids.

One helpful note: in studies, measured blood loss doesn't always match how women feel. If your period is disrupting your life, that alone is reason enough to treat it.

What you can do now

1. Track your cycle. Note start and end dates, heavy days, clots, and spotting. A few months of data makes your appointment far more useful.
2. Ask for the right labs. A complete blood count, ferritin, thyroid testing, and, if bleeding has always been heavy, screening for bleeding disorders.
3. Don't skip the evaluation if you're over 45 with irregular or heavy bleeding.
4. Support your iron. Eat iron-rich foods, pair them with vitamin C, and supplement if your ferritin is low.
5. Look at the bigger picture. Body weight affects estrogen levels and was linked to heavy bleeding in SWAN. Blood sugar, alcohol, and thyroid function all play a role too.

Heavy, unpredictable periods are common in perimenopause, but they're not something you have to plan your life around.

References

1. 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. View source
2. Changes in menstrual bleeding during perimenopause (SWAN and other cohorts, including short cycles and anovulation). View source
3. Harlow SD, et al. Abnormal uterine bleeding is associated with fatigue during the menopause transition. Menopause. 2025. Summary in EMJ. View source
4. American College of Obstetricians and Gynecologists. Practice Bulletin 128: Diagnosis of abnormal uterine bleeding in reproductive-aged women. Summary in MDedge. View source
5. Perimenopausal abnormal uterine bleeding. Contemporary OB/GYN. View source
6. Ultrasound or biopsy for evaluation of endometrium? It depends (ACOG 2019 expert analysis). MDedge. View source
7. Monash University Women's Health Research Program. Iron insufficiency in young Australian women. Summary in The Limbic. View source
8. Tools for Practice #323. How to slow the flow II: levonorgestrel intrauterine systems for heavy menstrual bleeding. Can Fam Physician. View source
9. Tools for Practice #348. How to slow the flow III: tranexamic acid for heavy menstrual bleeding. View source
10. PressHook. Menopause awareness: manage periods (search audit). View source