Periods that drag on longer than seven days have a wide range of causes, from hormonal shifts to structural changes in the uterus. A normal period lasts between three and seven days, with total blood loss under 80 mL (roughly five to six tablespoons). When bleeding consistently exceeds that window, something is usually driving the lining of the uterus to build up too thick, shed too slowly, or both.
Hormonal Imbalances
Your menstrual cycle depends on a precise back-and-forth between estrogen and progesterone. Estrogen thickens the uterine lining in the first half of your cycle, and progesterone stabilizes it after ovulation. If you don’t ovulate in a given cycle, progesterone never kicks in, and the lining keeps growing under estrogen’s influence. When it finally sheds, there’s simply more tissue to pass, so bleeding is heavier and lasts longer.
Several conditions disrupt this balance:
- Polycystic ovary syndrome (PCOS) frequently causes irregular or absent ovulation. Without regular progesterone production, the uterine lining can become unusually thick. Over time, this also raises the risk of abnormal cell changes in the lining.
- Thyroid disorders affect the hormones that regulate your cycle. Both an underactive and overactive thyroid can lead to prolonged or unpredictable bleeding, because thyroid hormones influence how quickly your body produces and clears estrogen and progesterone.
- High prolactin levels can suppress ovulation in a similar way. Prolactin is the hormone responsible for milk production, but elevated levels outside of breastfeeding interfere with the normal hormonal rhythm of your cycle.
Uterine Fibroids and Polyps
Fibroids are noncancerous growths in the muscular wall of the uterus. They’re extremely common, affecting up to 70 to 80 percent of women by age 50. When fibroids grow near the inner lining of the uterus, they increase the surface area that bleeds each month and can interfere with the uterus’s ability to contract and stop bleeding. The result is periods that last well beyond a week, often with heavy flow and clots.
Polyps are smaller, finger-like growths that develop on the uterine lining itself. They tend to cause spotting between periods and can extend the total number of days you see blood. Both fibroids and polyps are typically identified through ultrasound.
Adenomyosis
Adenomyosis happens when tissue that normally lines the uterus grows into the muscular wall. This causes the uterus to enlarge and become boggy, making it harder for the muscle to clamp down and stop menstrual bleeding. According to Mayo Clinic, heavy or long-lasting periods are one of the hallmark symptoms, along with severe cramping and a feeling of pressure in the lower abdomen. Some people with adenomyosis have no symptoms at all, while others find their periods debilitating.
Adenomyosis often overlaps with fibroids and endometriosis, which can make it tricky to pin down which condition is responsible for the prolonged bleeding.
Perimenopause and Life Stage Transitions
The years leading up to menopause, typically starting in your 40s but sometimes earlier, bring wide swings in estrogen and progesterone. Ovulation becomes unpredictable. You might skip it entirely for a cycle or two, then ovulate normally the next month. During cycles without ovulation, the lining builds up without the stabilizing effect of progesterone, and the resulting period can be noticeably longer or heavier than what you’re used to.
Adolescence works in a similar way. In the first year or two after a girl’s first period, the hormonal system is still maturing. Anovulatory cycles are common, and long, irregular periods are a normal part of that transition. Most teens settle into a more predictable pattern within two to three years.
Blood Clotting Disorders
Not all prolonged periods trace back to the uterus. Between 5 and 24 percent of women with chronic heavy menstrual bleeding have von Willebrand disease, a condition where the blood doesn’t clot properly. It’s the most common inherited bleeding disorder, yet it often goes undiagnosed because heavy periods are so frequently dismissed as normal.
Clues that a clotting disorder might be involved include heavy periods starting from your very first cycle, a history of prolonged bleeding after dental work or surgery, frequent nosebleeds, and easy bruising. If two or more of those apply, screening with a blood test is reasonable.
Medications That Extend Bleeding
Blood thinners are a well-documented cause of longer, heavier periods. Warfarin, apixaban, rivaroxaban, and dabigatran all work by interrupting the clotting process, and that effect doesn’t spare menstrual bleeding. Premenopausal women on these medications are especially at risk for abnormal uterine bleeding.
Hormonal IUDs and some types of hormonal contraceptives can cause prolonged spotting or bleeding in the first three to six months of use. Copper IUDs, which contain no hormones, tend to make periods heavier and longer as a baseline side effect. Certain antidepressants and corticosteroids can also alter cycle patterns, though less predictably.
Less Common but Serious Causes
Rarely, prolonged bleeding signals something more concerning. Endometrial hyperplasia, a precancerous thickening of the uterine lining, causes prolonged or irregular bleeding and is more common in women who have gone long stretches without ovulating. Endometrial cancer itself, while uncommon in younger women, typically presents with abnormal bleeding and is one reason persistent changes in your cycle deserve evaluation.
Infections of the uterus or cervix can also cause bleeding between or during periods that mimics a longer cycle. Cervical issues, including polyps or cellular changes, sometimes contribute to spotting that blurs the boundaries of a period.
How Long Periods Affect Your Health
The most immediate risk of consistently long periods is iron deficiency. Every cycle that runs over seven days or exceeds normal blood volume depletes your iron stores. The World Health Organization defines iron deficiency as a ferritin level below 15 micrograms per liter, though some guidelines use a threshold of 30. What makes this tricky is that your hemoglobin (the measure most people think of as “anemia”) can remain normal even when your iron stores are genuinely depleted. Many women experience fatigue, brain fog, hair thinning, and exercise intolerance from low iron long before they meet the technical definition of anemia.
If you’ve been told your bloodwork looks fine but you still feel exhausted, ask specifically about your ferritin level. A normal complete blood count doesn’t rule out iron deficiency on its own.
What to Track Before a Medical Visit
If your periods regularly last longer than seven days, keeping a record helps your provider identify the pattern faster. Note the number of days you bleed, how often you change pads or tampons (and how saturated they are), whether you pass clots, and any pain or other symptoms. Period tracking apps simplify this, but even a calendar with notes works well.
The causes range from easily treatable hormonal issues to conditions that benefit from imaging or lab work. A provider will typically start with blood tests to check hormone levels, thyroid function, and iron status, along with an ultrasound to look at the uterine lining and check for fibroids, polyps, or signs of adenomyosis. The pattern of your bleeding, your age, and your other symptoms narrow the list quickly.