A normal period lasts eight days or fewer. If yours has stretched to two weeks, something is causing your uterine lining to shed more slowly or more extensively than it should. The causes range from temporary hormonal shifts to structural changes in the uterus, and most are treatable once identified.
What Counts as Prolonged Bleeding
Medical guidelines define normal menstrual bleeding as eight days or less per cycle, with blood loss under about 80 mL total. A period lasting 14 days is nearly double the upper limit. One practical way to gauge severity: if you’re soaking through a pad or tampon in three hours or less, or passing clots larger than a quarter, the bleeding is considered heavy on top of being prolonged. That distinction matters because heavy, prolonged bleeding increases your risk of iron deficiency anemia, which can leave you dizzy, short of breath, and exhausted.
Hormonal Imbalances and Skipped Ovulation
The most common reason for a two-week period, especially if it’s a newer pattern, is a hormonal imbalance between estrogen and progesterone. Normally, after you ovulate, your body produces progesterone to stabilize the uterine lining. When ovulation doesn’t happen (called an anovulatory cycle), progesterone stays low while estrogen continues building up the lining. The result is a thicker, less stable lining that sheds unevenly and slowly, dragging your period out far longer than usual.
Polycystic ovary syndrome (PCOS) is one of the most common causes of this pattern. People with PCOS often don’t ovulate regularly, which leads to prolonged or unpredictable cycles. Stress, sudden weight changes, excessive exercise, and thyroid disorders can also disrupt ovulation enough to cause the same effect. A single anovulatory cycle can happen to anyone and isn’t necessarily a sign of a chronic problem, but if it keeps happening, there’s usually an identifiable cause.
Fibroids, Polyps, and Adenomyosis
Structural growths in the uterus are another leading explanation. These physical changes interfere with the uterus’s ability to contract and stop bleeding on schedule.
Uterine fibroids are noncancerous growths in the muscular wall of the uterus. There are several types. Submucosal fibroids, which grow into the inner cavity, are the most likely to cause prolonged or heavy bleeding because they distort the lining itself. Intramural fibroids grow within the uterine wall and can also extend periods by preventing the uterus from clamping down effectively.
Uterine polyps are soft growths that attach to the inner wall of the uterus, either by a broad base or a thin stalk. They’re estrogen-sensitive, meaning they grow in response to estrogen levels in your body. Polyps cause irregular bleeding, heavy flow, and bleeding between periods. They can range from a few millimeters to several centimeters.
Adenomyosis occurs when tissue that normally lines the inside of the uterus grows into the muscular wall. This makes the uterus thicker and heavier, and it tends to cause both prolonged bleeding and significant cramping. Adenomyosis is more common in your 30s and 40s, though it can happen earlier.
Birth Control Side Effects
If you recently started or changed a birth control method, that’s a likely culprit. Breakthrough bleeding is more common with low-dose and ultra-low-dose birth control pills, hormonal IUDs, and the implant. It’s also more frequent when you use pills or the ring on a continuous schedule to skip periods altogether.
The timeline for when this resolves depends on the method. With a hormonal IUD, spotting and irregular bleeding are common in the first months after placement but usually improve within two to six months. The implant works differently: whatever bleeding pattern you have in the first three months tends to be your pattern going forward. If extended bleeding on the implant hasn’t resolved by month three, it’s worth discussing alternatives with your provider.
Perimenopause
If you’re in your 40s (or sometimes late 30s), perimenopause is a strong possibility. During this transition, estrogen and progesterone rise and fall unpredictably. You may skip ovulation some months, which leads to the same kind of uneven, prolonged shedding described above. Periods can become longer, shorter, heavier, lighter, or skip entirely from one cycle to the next.
Perimenopause can last several years before menopause. While irregular periods are expected during this stage, bleeding that lasts longer than seven days, happens between periods, or is very heavy still warrants investigation. These symptoms overlap with conditions like polyps or fibroids that become more common with age, so it’s important not to write everything off as “just perimenopause.”
Thyroid Problems and Bleeding Disorders
An underactive thyroid (hypothyroidism) can quietly extend your periods. Thyroid hormones influence your entire metabolism, including how your body produces the proteins needed for blood clotting. In hypothyroidism, reduced protein synthesis can lower clotting factor levels enough to cause prolonged bleeding. In some cases, hypothyroidism has been directly linked to an acquired form of von Willebrand disease, a clotting disorder. Correcting the thyroid problem with medication resolves the clotting issue as well.
Inherited bleeding disorders can also be at play. Von Willebrand disease affects roughly 1% of the population and often goes undiagnosed in women because heavy periods are so commonly dismissed. If you’ve always had long, heavy periods and bruise easily, this is worth mentioning to your doctor.
What to Expect at the Doctor
If your period has lasted two weeks, especially if it’s heavy or this isn’t a one-time event, a doctor will typically start with a few straightforward steps. Blood work checks for iron deficiency anemia (from the prolonged blood loss), thyroid function, and clotting problems. A pelvic ultrasound uses sound waves to look for fibroids, polyps, or other structural changes in the uterus and ovaries.
If the ultrasound suggests something but doesn’t give a clear picture, the next step might be a sonohysterogram, where fluid is gently infused into the uterus to create a clearer ultrasound image of the lining. A hysteroscopy involves inserting a thin, lighted scope through the cervix to visually inspect the inside of the uterus. An endometrial biopsy, where a small tissue sample is taken from the lining, is done to rule out precancerous changes, particularly in women over 35 or those with risk factors.
None of these tests require general anesthesia in most cases, and many can be done in a single office visit. The goal is to identify a specific, treatable cause rather than just managing the symptom.
Signs the Bleeding Needs Urgent Attention
Prolonged bleeding on its own is concerning but not always an emergency. It becomes more urgent if you’re soaking through a pad or tampon every three hours or faster, passing large clots, feeling dizzy or lightheaded when you stand, noticeably pale, or experiencing a racing heartbeat at rest. These are signs of significant blood loss or anemia that may need treatment sooner rather than later. If you’re also experiencing severe pelvic pain or have any chance of pregnancy, those are additional reasons not to wait.