A normal period lasts between three and seven days. When bleeding consistently stretches beyond seven days, something is preventing your uterine lining from shedding efficiently and the bleeding from stopping on schedule. The causes range from simple hormonal shifts to underlying health conditions, and most of them are treatable once identified.
How Hormones Control Period Length
Your period length is largely dictated by two hormones: estrogen and progesterone. During the first half of your cycle, estrogen builds up the uterine lining. After ovulation, progesterone takes over, stabilizing that lining and preparing it for a possible pregnancy. If no pregnancy occurs, progesterone drops sharply, which triggers the blood vessels supplying the lining to constrict and cut off blood flow. The lining breaks down in an organized way and sheds as your period.
When progesterone is too low or absent, this process goes sideways. Without enough progesterone to stabilize it, the lining keeps growing under estrogen’s influence, becoming thicker and more fragile. When it finally breaks down, the shedding is disorganized, heavier, and takes longer to complete. This hormonal imbalance is the single most common thread connecting many of the causes below.
Skipped Ovulation
If you don’t ovulate during a cycle, your body never produces the progesterone surge that normally follows. The result is what’s called “unopposed estrogen,” where the uterine lining keeps thickening with no hormonal signal to stop it. When it eventually sheds, the bleeding tends to be unpredictable, heavy, and prolonged.
Polycystic ovary syndrome (PCOS) is the most common cause of chronic skipped ovulation. But anovulatory cycles also happen during times of high stress, significant weight changes, excessive exercise, or illness. Even women with otherwise regular cycles skip ovulation occasionally, which can produce a one-off period that drags on longer than usual. The high estrogen levels also increase vascular fragility in the uterine lining, contributing to heavier flow on top of the longer duration.
Perimenopause
If you’re in your late 30s or 40s and your periods are getting longer, perimenopause is a likely explanation. During the menopausal transition, 77% of women experience at least three episodes where bleeding lasts 10 or more days. This happens because hormone levels become increasingly erratic. In early perimenopause, cycles often get shorter (under 21 days), while later in the transition they stretch out beyond 36 days. Ovulation becomes less reliable, and the same unopposed-estrogen pattern described above takes hold during anovulatory cycles.
Interestingly, while periods may last longer during perimenopause, they don’t necessarily get heavier overall. The general trend is actually toward lighter flow as you approach menopause. If your periods are both significantly longer and significantly heavier during this time, that warrants a closer look for other causes.
Uterine Fibroids and Polyps
Fibroids (noncancerous growths in or on the uterus) and endometrial polyps are structural causes of longer periods. Fibroids can distort the uterine cavity, increase the surface area of the lining, and interfere with the uterus’s ability to contract and clamp down on blood vessels after shedding begins. Polyps, which are small overgrowths of the uterine lining, create areas that bleed irregularly.
Both are extremely common. Fibroids affect up to 70-80% of women by age 50, though many cause no symptoms. When they do cause bleeding problems, the location matters more than the size. Fibroids that protrude into the uterine cavity (submucosal fibroids) are the most likely to extend period length and increase flow.
Adenomyosis
Adenomyosis occurs when tissue from the uterine lining grows into the muscular wall of the uterus. This causes the uterus to enlarge and makes it harder for it to contract effectively during your period. The result is prolonged bleeding, heavy flow, and often significant cramping. It’s most common in women in their 30s and 40s, and it frequently coexists with fibroids, which can make pinpointing the cause more complicated.
The Copper IUD
If your periods got longer after getting a copper (non-hormonal) IUD, you’re far from alone. In a study of over 600 copper IUD users, 50% reported an increase in the number of bleeding days and 60% reported heavier flow. Objective measurements from research using collected sanitary products show that copper IUDs increase menstrual blood loss by about 50% over pre-insertion levels, and this increase stays relatively constant through at least the first 12 months of use.
Many women hope the bleeding will settle down after the first few months, and while the subjective perception of heavy bleeding may improve, the actual blood loss measured in studies does not appear to decrease meaningfully in the first year.
Thyroid Problems
An underactive thyroid (hypothyroidism) is linked to both heavier and longer periods. Thyroid hormones influence the production of sex hormones including progesterone. Lower thyroid hormone levels are associated with lower progesterone throughout the cycle, particularly during the first half. This circles back to the same core issue: without adequate progesterone, the lining doesn’t stabilize properly and shedding takes longer.
Thyroid disorders are easily identified with a blood test and highly treatable. If longer periods are accompanied by fatigue, weight gain, cold sensitivity, or dry skin, thyroid function is worth checking.
Bleeding Disorders
Between 5% and 20% of women with chronically heavy or prolonged periods have an underlying bleeding disorder, most commonly von Willebrand disease. This condition affects the blood’s ability to clot, which means that once the uterine lining starts shedding, bleeding takes longer to stop. Many women with mild bleeding disorders go undiagnosed for years because they assume their periods are just “naturally heavy.” If you’ve also experienced easy bruising, prolonged bleeding from cuts, or heavy bleeding after dental work or surgery, a bleeding disorder could be the cause.
What Helps Shorten Prolonged Periods
Treatment depends entirely on the underlying cause, but several options can reduce both the duration and volume of bleeding. Anti-inflammatory pain relievers like ibuprofen, taken during your period, can reduce blood loss by roughly 20-25%. A prescription medication that helps blood clot more effectively at the uterine lining can reduce menstrual blood loss by 26-60% in clinical studies, making it one of the most effective non-hormonal options.
Hormonal approaches work by addressing the root progesterone deficit. Birth control pills regulate the cycle and thin the lining. A hormonal IUD is particularly effective, reducing menstrual blood loss by 83% within three months, 88% at six months, and 96% at one year in clinical trials. For structural problems like fibroids or polyps, removing them often resolves the bleeding.
If your periods consistently last more than seven days, involve clots larger than a quarter, or require you to change a pad or tampon every hour or two, these are signs of genuinely excessive bleeding rather than normal variation. Both blood clots and bleeding beyond seven days are independent predictors of clinically significant blood loss.