A normal period lasts between three and seven days. If your bleeding regularly stretches beyond seven days, something is shifting your hormonal balance, affecting your uterine lining, or interfering with how your blood clots. The cause can be as straightforward as a new IUD or as subtle as chronic stress, and most of the common reasons are very treatable once identified.
What Counts as a Longer-Than-Usual Period
Most people bleed for three to seven days during each cycle, with cycles repeating every 21 to 35 days. A period that consistently lasts more than seven days falls outside the normal range. The occasional longer period, especially during a stressful month or after a change in birth control, isn’t necessarily a sign of trouble. But if the pattern repeats for two or three cycles in a row, it’s worth looking into.
Hormonal Shifts and Perimenopause
The most common reason for a period that suddenly starts lasting longer is a change in your hormone levels, specifically estrogen and progesterone. These two hormones control how thick your uterine lining grows each month and when it sheds. When they fall out of their usual rhythm, your lining can build up more than normal and take longer to shed completely.
If you’re in your late 30s or 40s, perimenopause is a likely explanation. During this transition, estrogen rises and falls unpredictably instead of following its usual pattern. Your periods may get longer, shorter, heavier, or lighter from one month to the next. One early sign of perimenopause is a menstrual cycle length that shifts by seven days or more compared to your usual pattern. This phase can last several years before periods stop entirely, and the irregularity tends to increase over time.
Stress and Its Effect on Your Cycle
Your brain controls your menstrual cycle through a chain of hormonal signals that starts in the hypothalamus and pituitary gland. Stress, whether emotional, physical, or nutritional, triggers a rise in cortisol that can interrupt this signaling chain. The result is a disrupted cycle: your body may delay or skip ovulation entirely, which throws off the timing and duration of your period. When ovulation doesn’t happen on schedule, the uterine lining continues to build without the progesterone signal that normally stabilizes it. When it finally does shed, the process takes longer and the bleeding can be heavier.
Your IUD or Other Birth Control
A copper IUD is one of the most predictable causes of longer, heavier periods. Because it contains no hormones, it works by creating a low-level inflammatory response in the uterus, which can make periods heavier, longer, and crampier, especially in the first few months after insertion. For many people this settles down over time, but for some it persists.
Hormonal IUDs work differently. They typically cause irregular, light bleeding for the first three to six months, which can feel like a drawn-out period even though the total blood loss is usually small. Other hormonal methods, like the shot or the implant, can also cause prolonged spotting or bleeding as your body adjusts.
Thyroid Problems
Your thyroid gland produces hormones that influence nearly every system in your body, including your reproductive system. When thyroid hormone levels drop too low (hypothyroidism), two things happen that can extend your period. First, low thyroid hormone changes how your blood clots, which can lead to heavier bleeding that takes longer to stop. Second, your uterine lining may thicken excessively and then shed unpredictably. Other signs of an underactive thyroid include fatigue, weight gain, feeling cold, and dry skin. A simple blood test can confirm the diagnosis.
Uterine Fibroids and Adenomyosis
Fibroids are noncancerous growths in or on the uterine wall. Depending on their size and location, they can increase the surface area of the uterine lining, leading to longer and heavier periods. They’re extremely common, particularly after age 30.
Adenomyosis is a related condition where tissue that normally lines the uterus grows into the muscular wall of the uterus itself. This causes the uterus to enlarge and can lead to heavy, prolonged periods with severe cramping. Adenomyosis often occurs alongside fibroids or endometriosis, which can make pinpointing the exact cause more complicated since the symptoms overlap. Imaging tests like ultrasound or MRI help distinguish between them.
Bleeding Disorders
This is one of the most underdiagnosed causes of long or heavy periods. Von Willebrand disease, a condition where the blood doesn’t clot properly, affects between 5% and 24% of women with chronic heavy menstrual bleeding. Many of these women go years without a diagnosis because heavy periods are often dismissed as “just how things are.” If your periods have always been long and heavy, starting from your very first cycle, and you also bruise easily, bleed a lot from minor cuts, or have had excessive bleeding after dental work or surgery, a bleeding disorder is worth investigating.
Endometriosis
Endometriosis occurs when tissue similar to the uterine lining grows outside the uterus, on organs like the ovaries, fallopian tubes, or the tissue lining the pelvis. While its hallmark symptom is pain (especially during periods and sex), it can also contribute to longer periods. The inflammatory environment it creates can disrupt normal hormonal patterns and affect how the uterine lining behaves during your cycle.
Signs That Deserve Prompt Attention
Some patterns of prolonged bleeding signal that you’re losing enough blood to affect your health. You should be evaluated if you’re soaking through a pad or tampon every hour for several hours in a row, passing blood clots the size of a quarter or larger, needing to double up on pads, or waking up at night to change protection. Fatigue, shortness of breath, and feeling lightheaded are signs of anemia from blood loss and shouldn’t be ignored.
A single period that runs a day or two long isn’t usually cause for concern. But bleeding that consistently lasts more than seven days, keeps you from your normal activities, or comes with severe pain points to something that’s identifiable and, in most cases, fixable.