A normal period lasts 4 to 5 days, and anything beyond 7 days is considered prolonged bleeding. If your period is dragging on longer than usual, the cause could be as simple as a hormonal fluctuation or as significant as a thyroid condition or uterine growth. The good news is that most causes are treatable once identified.
How Long Is Too Long?
Most people lose only about 2 to 3 tablespoons of blood during a typical period. Bleeding that lasts more than 7 days, or that’s heavy enough to soak through a pad or tampon nearly every hour, crosses the threshold into what’s clinically called heavy menstrual bleeding (menorrhagia). Blood loss of 80 mL or more per cycle is the formal cutoff, but you don’t need to measure. If your period is significantly longer or heavier than your personal normal, that’s worth paying attention to.
Hormonal Imbalances
The most common reason for a period that won’t quit is a hormonal one. Your cycle depends on a precise back-and-forth between estrogen and progesterone. Estrogen builds up the uterine lining in the first half of your cycle, and progesterone stabilizes it after ovulation. When you don’t actually ovulate (which can happen without you realizing it), progesterone stays low. The lining keeps building under estrogen’s influence, then sheds unevenly and incompletely, leading to prolonged or erratic bleeding.
These cycles without proper ovulation are surprisingly common. They happen more frequently during times of hormonal transition, like puberty and perimenopause, but can also be triggered by stress, significant weight changes, excessive exercise, or conditions like polycystic ovary syndrome (PCOS). With PCOS, the ovaries often don’t release eggs regularly, so progesterone remains low and periods become unpredictable, sometimes absent for weeks and then prolonged when they finally arrive.
Thyroid Problems
Your thyroid gland plays a bigger role in your menstrual cycle than most people realize. An underactive thyroid (hypothyroidism) disrupts both cycle length and bleeding volume. In studies of women with overt hypothyroidism, about 26% experienced periods lasting longer than a week, and another 26% had cycles spaced more than 35 days apart. In women with severe hypothyroidism, those numbers rose to 35% for both prolonged bleeding and irregular cycle spacing.
If your period changes come alongside fatigue, weight gain, feeling cold all the time, or dry skin, a simple blood test can check your thyroid function. Treating the thyroid issue typically brings periods back to normal.
Uterine Fibroids and Polyps
Structural growths inside the uterus are another frequent culprit. Uterine polyps are soft tissue growths that attach to the inner wall of the uterus, ranging from sesame-seed-sized to as large as a golf ball. They cause irregular bleeding, very heavy flow, and spotting between periods. Fibroids are muscular growths in or on the uterine wall that can distort the lining, increase its surface area, and interfere with the uterus’s ability to contract and stop bleeding efficiently.
Both are extremely common, especially in your 30s and 40s. Neither is typically cancerous, but both can make periods significantly longer and heavier. An ultrasound is usually all that’s needed to spot them.
Birth Control Side Effects
If you recently started or switched a hormonal contraceptive, that’s a likely explanation. Breakthrough bleeding is one of the most common side effects of both the pill and hormonal IUDs, particularly in the early months.
With combined oral contraceptives, unscheduled bleeding occurs in roughly 10 to 18% of cycles. It’s most common in the first 3 to 4 months and generally decreases after that. With hormonal IUDs, irregular bleeding is even more frequent early on: 35% of users report prolonged or frequent bleeding episodes in the first six months. The pattern improves dramatically with time. Only about 4% of IUD users still experience excessive bleeding after 12 months, and roughly half eventually stop getting periods altogether.
If you’re within the first few months of a new method, patience is usually the right approach. If the bleeding persists past the 6-month mark or is very heavy, it’s worth a follow-up.
Perimenopause
If you’re in your 40s, perimenopause is one of the most likely explanations for a period that’s behaving strangely. The transition to menopause brings increasingly erratic cycles as ovulation becomes less reliable. Average cycle length jumps from about 30 days (four years before menopause) to over 80 days in the final year before periods stop entirely. Long, unpredictable cycles occur throughout perimenopause, but the most dramatic shifts happen in that last year.
During this time, individual periods can also last longer than usual. When ovulation is skipped, estrogen continues to build the uterine lining without progesterone to keep it in check, and the eventual bleed can be heavy and prolonged. This is a normal part of the transition, but heavy or prolonged bleeding during perimenopause still deserves evaluation to rule out polyps, fibroids, or changes to the uterine lining.
Bleeding Disorders
About 10 to 12% of women with unexplained heavy periods turn out to have an inherited bleeding disorder. The most common is von Willebrand disease, a condition where the blood doesn’t clot properly. Among women with heavy periods who are found to have a bleeding disorder, more than half have von Willebrand disease specifically.
Clues that a bleeding disorder might be involved include heavy periods that started right from your very first cycle, a history of easy bruising, prolonged bleeding after dental work or surgery, or family members with similar issues. This is often missed for years because heavy periods get attributed to other causes first.
Signs You’re Losing Too Much Blood
A prolonged period isn’t just inconvenient. Ongoing blood loss can lead to iron-deficiency anemia, sometimes gradually enough that you don’t notice until it’s significant. Watch for persistent tiredness that doesn’t improve with rest, weakness, shortness of breath during activities that didn’t used to wind you, dizziness or lightheadedness, pale skin, cold hands and feet, or headaches. An irregular or rapid heartbeat can develop when anemia becomes more severe, because the heart has to work harder to compensate for reduced oxygen in the blood.
What Treatment Looks Like
Treatment depends entirely on what’s causing the prolonged bleeding. Hormonal options, like certain types of birth control, work by stabilizing the uterine lining and regulating the cycle. A hormonal IUD is one of the most effective tools for heavy bleeding, reducing blood loss by 83 to 96% over the first year.
For non-hormonal options, medications that help blood clot more effectively can reduce menstrual blood loss by 26 to 60% when taken during your period. Anti-inflammatory pain relievers also have a modest effect, reducing flow by about 20 to 25%. If fibroids or polyps are the cause, removing them often resolves the problem. Thyroid treatment, managing PCOS, or addressing a bleeding disorder each target the root cause directly.
The first step is figuring out which category your situation falls into. That typically involves a physical exam, blood work (checking for anemia, thyroid function, and clotting issues), and often an ultrasound. From there, the path forward is usually straightforward.