A normal period lasts between 2 and 7 days. If yours regularly stretches beyond that window, something is keeping your uterine lining from shedding efficiently, whether that’s a hormonal imbalance, a physical change in the uterus, or an underlying health condition. The good news is that most causes of prolonged periods are identifiable and treatable.
What Counts as a Long Period
Anything over 7 days is considered prolonged bleeding. But even within that 2-to-7-day range, there’s a lot of variation from person to person and cycle to cycle. A period that lasts 6 days isn’t a problem on its own. What matters more is whether your pattern has changed, whether you’re soaking through a pad or tampon every hour for multiple hours in a row, or whether you’re passing clots larger than a quarter. Those are signs the bleeding is both long and heavy, a combination that deserves attention.
Hormonal Imbalance Is the Most Common Cause
Your period depends on a precise back-and-forth between estrogen and progesterone. During the first half of your cycle, estrogen thickens the uterine lining. After ovulation, progesterone stabilizes that lining and, when levels drop, triggers a clean, organized shed. That shed is your period.
When you don’t ovulate in a given cycle, progesterone never kicks in. Estrogen keeps building the lining with nothing to counterbalance it. The medical term for this is “unopposed estrogen.” The lining grows thicker and more disorganized than usual, and when it finally breaks down, it sheds unevenly and over a longer stretch of time. Instead of a tidy 4- or 5-day bleed, you get spotting that drags on, or heavy bleeding that starts and stops unpredictably.
This is exactly what happens in polycystic ovary syndrome (PCOS), which is the most common hormonal cause of long, irregular periods. About 85 to 90% of women with infrequent periods have PCOS. The hallmark is cycles longer than 35 days, caused by infrequent or absent ovulation. When a period does finally arrive, it can be heavy and prolonged because the lining has been building for weeks without progesterone to regulate it.
Fibroids and Polyps
Uterine fibroids are noncancerous growths in the muscular wall of the uterus, and they’re remarkably common. They cause longer, heavier periods through several mechanisms: they increase the surface area of the uterine lining, they interfere with the uterus’s ability to contract and squeeze blood vessels shut during a period, and they can compress veins in the uterine wall, causing blood to pool. Submucosal fibroids, the type that grows into the uterine cavity, tend to cause the most bleeding problems.
Polyps work similarly. These are small, soft growths on the inner lining of the uterus. They create extra surface area that bleeds, and they can prevent the uterus from contracting down fully after shedding its lining. Both fibroids and polyps can be identified with an ultrasound.
The Copper IUD Effect
If your periods got longer after getting a copper (non-hormonal) IUD, you’re not imagining it. In one study of over 600 copper IUD users, 50% reported an increase in the number of bleeding days. At 3 months after insertion, about 24% of women experienced prolonged bleeding. The encouraging part: by 12 months, that number dropped to 0% in one smaller study, suggesting the body adjusts over time. The average number of bleeding days held relatively steady at around 5 to 6 across the first year, though some women who couldn’t tolerate the side effects had the device removed earlier.
Perimenopause Changes Everything
If you’re in your 40s (or sometimes late 30s) and your periods are getting longer, shorter, heavier, lighter, or just plain unpredictable, perimenopause is a likely explanation. During this transition, estrogen levels rise and fall erratically rather than following the smooth, predictable pattern of earlier reproductive years. You may skip ovulation in some cycles, which creates the same unopposed estrogen situation described above.
Early perimenopause often shows up as cycles that vary by 7 or more days from one month to the next. Late perimenopause is marked by gaps of 60 days or more between periods. When a period does come after a long gap, the lining has had extra time to build up, so the bleed can be heavier and longer than what you’re used to.
Bleeding Disorders
About 10 to 12% of women with consistently heavy, prolonged periods have an inherited bleeding disorder. The most common is von Willebrand disease, a condition where the blood doesn’t clot as efficiently as it should. Many women with mild bleeding disorders go undiagnosed for years because they assume their heavy periods are just their normal. If you’ve always had long, heavy periods, if you bruise easily, or if you’ve had prolonged bleeding after dental work or minor injuries, a bleeding disorder is worth investigating with a blood test.
Thyroid Problems
An underactive thyroid (hypothyroidism) has long been linked to menstrual irregularities, including heavier and more frequent periods. The relationship is real but more nuanced than often described. One longitudinal study found that thyroid hormone levels had little measurable effect on actual bleed length or intensity. The bigger impact seems to be on cycle regularity and overall menstrual pattern rather than on how many days you bleed. Still, if prolonged periods come alongside fatigue, weight gain, cold sensitivity, or dry skin, thyroid screening is a reasonable step.
Why Long Periods Matter Beyond Inconvenience
A period that drags on isn’t just annoying. Women with heavy menstrual bleeding lose five to six times more iron per cycle than women with normal flow. Over months or years, this depletes your iron stores and can lead to iron-deficiency anemia, which shows up as exhaustion, brain fog, shortness of breath during routine activity, and pale skin. Heavy menstrual bleeding is defined as losing more than 80 mL of blood per cycle, roughly equivalent to soaking through 16 regular tampons over the course of a period. If you’re regularly going through significantly more than that, your iron levels are likely taking a hit even if you haven’t been formally diagnosed with anemia.
Persistent unopposed estrogen also carries its own risk. When the uterine lining builds up cycle after cycle without progesterone to regulate it, the cells can become abnormal over time, a condition called endometrial hyperplasia. Most cases are benign, but some can progress. This is one reason prolonged, irregular bleeding shouldn’t be dismissed indefinitely as “just how my body works.”
Signs That Need Prompt Attention
Soaking through at least one pad or tampon every hour for more than two consecutive hours is a sign of bleeding that may need urgent evaluation. The same goes for bleeding between periods, passing clots larger than a quarter regularly, or any vaginal bleeding after menopause. These don’t automatically mean something serious, but they cross the threshold where investigation is warranted rather than optional.