A normal period lasts about 4 to 5 days, with total blood loss of roughly 2 to 3 tablespoons. When bleeding stretches beyond 7 days, it crosses into what’s clinically considered a prolonged or heavy period. The causes range from temporary hormonal shifts to underlying conditions that need treatment.
How Hormonal Imbalance Extends Bleeding
The most common reason for longer periods is an imbalance between estrogen and progesterone, the two hormones that control your menstrual cycle. Estrogen thickens the uterine lining each month to prepare for a possible pregnancy. After ovulation, progesterone rises and stabilizes that lining. If pregnancy doesn’t happen, both hormones drop, and the lining sheds as your period.
When you don’t ovulate in a given cycle, progesterone never kicks in. Without it, estrogen keeps building the lining unchecked, making it much thicker than usual. When that overgrown lining finally breaks down, there’s simply more tissue to shed, which means heavier flow and more days of bleeding. This type of “unopposed estrogen” effect can also cause the lining cells to crowd together abnormally, a condition called endometrial hyperplasia. It’s one of the most frequent explanations for periods that drag on well past a week.
Uterine Conditions That Prolong Periods
Two structural problems in the uterus are particularly known for making periods longer: fibroids and adenomyosis.
Fibroids are noncancerous growths in or on the uterine wall. Depending on their size and location, they can distort the uterine lining and increase the surface area that bleeds during your period. Submucosal fibroids, the type that grow just beneath the lining, tend to cause the most significant changes in flow and duration.
Adenomyosis happens when tissue that normally lines the inside of the uterus starts growing into the muscular wall itself. During your period, that embedded tissue also thickens, breaks down, and bleeds, just like the normal lining does. The result is a uterus that’s essentially bleeding from within its own walls on top of the regular shedding happening at the surface. This often leads to painful, prolonged periods and can make the uterus noticeably larger over time. Adenomyosis is most common in women in their 30s and 40s, especially those who have had children.
Endometrial polyps, small overgrowths on the uterine lining, can also cause bleeding between periods or extend the length of a period. They’re usually benign but can cause persistent spotting that makes it seem like your period never fully stops.
Thyroid Problems and Period Length
An underactive thyroid (hypothyroidism) can quietly extend your periods through several overlapping mechanisms. Low thyroid hormone disrupts the communication between your brain and your ovaries. Specifically, when the thyroid underperforms, the pituitary gland overproduces thyroid-stimulating hormone (TSH) to compensate. That overproduction creates a ripple effect: it raises prolactin levels, suppresses the hormones that trigger ovulation, and can even mildly stimulate estrogen production on its own.
The end result looks a lot like the hormonal imbalance described above: estrogen stays elevated without progesterone to balance it, the uterine lining overgrows, and bleeding becomes heavier and longer. On top of that, hypothyroidism impairs your blood’s ability to clot normally. It can cause a form of platelet dysfunction similar to von Willebrand disease, making it harder for bleeding to stop once it starts. Even subclinical hypothyroidism, where symptoms are mild and blood tests are only slightly off, can affect menstrual patterns.
Bleeding Disorders
Some women bleed longer simply because their blood doesn’t clot efficiently. Von Willebrand disease is the most common inherited bleeding disorder, and it’s significantly underdiagnosed in women. Among those with chronically heavy or prolonged periods, somewhere between 5% and 24% turn out to have von Willebrand disease. The prevalence varies by ethnicity: roughly 16% among white women with heavy bleeding compared to about 1.3% among Black women.
If your periods have been long and heavy since your very first one, or if 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. It’s the kind of cause that often gets missed for years because heavy periods are so frequently attributed to hormonal issues alone.
Perimenopause and Puberty
The two life stages when longer periods are most predictable are the beginning and the end of your reproductive years. During puberty, the hormonal system is still calibrating. Irregular ovulation is normal in the first couple of years after your first period, which means cycles can be unpredictable in both timing and duration.
Perimenopause, the transition leading up to menopause, creates a similar kind of hormonal instability but for the opposite reason: the system is winding down. Estrogen rises and falls erratically, ovulation becomes unpredictable, and you may skip it entirely in some cycles. When that happens, the lining builds without progesterone’s stabilizing effect, and the eventual period can be notably heavier and longer. Some cycles might be short and light while the next one lasts 10 days. This phase typically begins in your 40s and can last several years.
Copper IUDs and Medications
If your periods got longer after getting a copper IUD, that’s a well-documented side effect. The copper IUD contains no hormones and instead works by creating an inflammatory response in the uterus that prevents pregnancy. That same inflammation tends to make periods heavier, longer, and more crampy, especially in the first few months. These side effects typically ease up after three to six months, though some women find their periods remain somewhat heavier for as long as the device is in place.
Certain medications can also extend bleeding. Blood thinners (anticoagulants) reduce your blood’s ability to clot, which directly translates to longer, heavier periods. Anti-inflammatory painkillers like aspirin and ibuprofen affect platelet function as well, though their impact on period length is usually more modest. If you recently started a new medication and noticed your periods getting longer, the timing is worth mentioning to your provider.
Signs Your Bleeding Needs Attention
Not every long period is cause for alarm, especially if it’s a one-off. But certain patterns signal that something more is going on. Soaking through a pad or tampon every hour for several consecutive hours is a red flag. So is needing to double up on pads, waking at night to change protection, or passing blood clots the size of a quarter or larger. Periods consistently lasting more than 7 days also warrant evaluation.
Prolonged heavy bleeding can lead to iron-deficiency anemia over time. If you’re feeling unusually fatigued, short of breath during normal activities, or lightheaded, those symptoms may be connected to chronic blood loss rather than being separate issues. A simple blood count can confirm whether your iron stores are depleted, and identifying the underlying cause of the longer periods is the first step toward getting them back to a manageable length.