A normal period lasts 4 to 5 days, and anything beyond 7 days is classified as prolonged bleeding. If your period has gone past that threshold, or it feels like it’s dragging on without tapering off the way it usually does, something is disrupting the normal process of shedding your uterine lining. The causes range from minor and temporary to conditions that need treatment, and figuring out which category you fall into depends on a few key details.
What Counts as a Period That’s Too Long
The CDC defines heavy menstrual bleeding as periods lasting more than 7 days or requiring a new pad or tampon in less than 2 hours. Passing large clots or soaking through one or more pads every hour for several hours in a row also qualifies. If your period is simply a day or two longer than your personal normal but light, that’s less concerning than a period that stays heavy past the one-week mark.
The volume matters as much as the duration. A typical period involves losing about 2 to 3 tablespoons of blood total. Women with prolonged, heavy bleeding often lose twice that amount or more, which can lead to iron-deficiency anemia over time. Fatigue, dizziness, and feeling short of breath during your period are signs your blood loss may be significant enough to affect your health.
Hormonal Imbalances Are the Most Common Cause
Your period ends because, after ovulation, your body produces progesterone to stabilize the uterine lining. When progesterone drops at the end of the cycle, the lining sheds in a controlled way. If you don’t ovulate in a given cycle, progesterone never rises, and estrogen keeps building up the lining without anything to regulate it. The result is a lining that grows too thick and then sheds unevenly, often for longer and heavier than normal.
This is exactly what happens with polycystic ovary syndrome (PCOS). Sustained high estrogen combined with low progesterone from irregular or absent ovulation creates cycles where bleeding can drag on for weeks. It also happens during perimenopause, when ovulation becomes unpredictable. Women in late perimenopause may go 60 days or more between periods and then experience heavy, prolonged bleeding (sometimes called “flooding”) when a period finally arrives. Stress, significant weight changes, and overexercise can all disrupt ovulation in a similar way, even without an underlying condition.
Thyroid Problems and Clotting Disorders
An underactive thyroid (hypothyroidism) can cause prolonged or heavy periods through two separate mechanisms. First, low thyroid hormone suppresses the signals your brain sends to your ovaries, disrupting ovulation the same way PCOS does. Second, a lack of thyroid hormone changes how your blood clots, which can make bleeding heavier and harder to stop. Your uterine lining may also thicken excessively and shed unpredictably. An overactive thyroid tends to do the opposite, making periods lighter or shorter.
Bleeding disorders are an underrecognized cause. Among women with chronic heavy menstrual bleeding, 5% to 24% have an underlying clotting disorder, most commonly von Willebrand disease. This condition reduces your blood’s ability to clot efficiently, so normal menstrual bleeding simply takes longer to stop. If your periods have always been heavy since your very first one, or you also bruise easily and bleed a long time from minor cuts, a clotting disorder is worth investigating.
Structural Problems in the Uterus
Fibroids (noncancerous growths in the uterine wall) and polyps (small growths on the uterine lining) physically increase the surface area that bleeds during your period. They can also interfere with the uterus’s ability to contract and clamp down on blood vessels, which is how bleeding normally stops.
Adenomyosis is a related condition where tissue similar to the uterine lining grows into the muscular wall of the uterus. This causes the uterus to thicken and enlarge, sometimes to double or triple its usual size. The extra tissue bleeds during your period just like the normal lining does, extending and intensifying bleeding. Because estrogen drives this tissue growth, adenomyosis symptoms often improve after menopause.
Birth Control and Medications
If you recently started a new contraceptive, that may be the explanation. The copper IUD is well known for causing heavier, longer periods, especially in the first three to six months after insertion. Some people report irregular bleeding for several months. Hormonal implants and new hormonal IUDs can also cause prolonged spotting or bleeding as your body adjusts, though this typically settles within a few months.
Certain medications can extend bleeding as well. Blood thinners (anticoagulants) reduce your blood’s ability to clot, directly prolonging menstrual bleeding the same way a clotting disorder would. Even common over-the-counter pain relievers like aspirin can have this effect, since aspirin thins the blood. NSAIDs like ibuprofen and naproxen, while sometimes used to reduce menstrual flow, can also alter bleeding patterns in some people.
How Prolonged Bleeding Gets Evaluated
If your period consistently lasts beyond 7 days or you’re experiencing a one-off episode that won’t stop, the typical workup starts with blood tests. These check for anemia, thyroid function, and hormone levels. For women over 45, or younger women with risk factors like obesity or PCOS, a tissue sample from the uterine lining is recommended as a first-line test to rule out abnormal cell growth.
A pelvic ultrasound can identify structural causes like fibroids, polyps, or adenomyosis. If initial blood work suggests a clotting problem, more specific testing for von Willebrand disease and related conditions follows. The goal is to sort your bleeding into one of the categories above, because treatment depends entirely on the underlying cause. Hormonal imbalances are typically managed with hormonal therapy to regulate your cycle, while structural problems may need a procedure, and thyroid issues resolve with thyroid treatment.
Signs You Need Urgent Care
Most prolonged periods are not emergencies, but some are. If you’re soaking through two or more pads or tampons every hour for two to three hours straight, that level of blood loss requires prompt medical attention. The same applies if you feel lightheaded, dizzy, or short of breath during your period. These are signs of significant blood loss that can lead to anemia, which can become dangerous without treatment.
Even if your bleeding isn’t at emergency levels, a period that has continued for more than 10 to 14 days without signs of slowing warrants a call to your doctor. Persistent low-grade bleeding may not feel urgent, but it can quietly deplete your iron stores over time, leaving you exhausted and increasingly symptomatic with each cycle.