Abnormal bleeding is any uterine bleeding that falls outside the pattern of a typical menstrual cycle, whether it’s heavier than normal, lasts longer than seven days, occurs between periods, or happens after menopause. It’s one of the most common reasons people visit a gynecologist, and while many causes are benign and treatable, some require prompt evaluation.
What Counts as Abnormal
A typical period lasts between three and seven days and follows a roughly predictable cycle. Bleeding qualifies as abnormal when it breaks that pattern in specific ways: periods lasting longer than seven days, flow heavy enough to soak through a pad or tampon every hour for several consecutive hours, needing to change protection in less than two hours, or passing large clots. Spotting or bleeding between periods, bleeding during or after sex, and any bleeding after menopause also fall into this category.
The distinction matters because these patterns point to different underlying problems. Someone soaking through a pad every hour faces a different set of possible causes than someone with light but persistent spotting between otherwise normal periods.
Common Causes by Age Group
Teens and Young Adults
Irregular bleeding is extremely common in adolescents because the hormonal system that controls ovulation hasn’t fully matured yet. When the brain, pituitary gland, and ovaries aren’t yet coordinating smoothly, ovulation can be skipped. Without ovulation, the body doesn’t produce progesterone on schedule, and the uterine lining builds up unevenly before shedding in unpredictable, sometimes heavy episodes. For most teens, cycles gradually regulate on their own, though it can take a few years.
Reproductive Years
In people between roughly 20 and 45, the causes broaden considerably. The International Federation of Gynecology and Obstetrics organizes them into two groups: structural problems in the uterus and non-structural problems throughout the body. The structural causes include polyps (small growths on the uterine lining), adenomyosis (where lining tissue grows into the uterine wall), fibroids (benign muscle tumors), and, less commonly, precancerous or cancerous changes. Non-structural causes include clotting disorders, problems with ovulation, hormonal imbalances, and side effects from medications or devices like IUDs.
Hormonal contraception is one of the most frequent culprits behind spotting between periods. Starting, stopping, or inconsistently using birth control pills, patches, or rings can trigger breakthrough bleeding. Cervical infections and inflammation can also cause spotting, particularly after intercourse.
After Menopause
Any bleeding that occurs 12 or more months after your final period is considered postmenopausal bleeding and always warrants investigation. About 9% of postmenopausal women who see a doctor for bleeding are ultimately diagnosed with endometrial cancer, with rates ranging from around 5% in North America to 13% in Western Europe. That means the large majority of cases have a non-cancerous explanation, such as thinning of the vaginal or uterine lining, polyps, or hormone therapy effects. But the 9% figure is high enough that no postmenopausal bleeding should be dismissed.
Roughly 90% of people diagnosed with endometrial cancer had postmenopausal bleeding as their first symptom. Early detection makes a significant difference in outcomes, which is why guidelines have recently shifted toward more aggressive initial testing.
Why Hormonal Imbalance Causes Heavy Bleeding
To understand why so many causes of abnormal bleeding trace back to hormones, it helps to know what’s supposed to happen. In a normal cycle, estrogen builds up the uterine lining during the first half, then progesterone stabilizes and organizes it during the second half. When pregnancy doesn’t occur, progesterone drops, the lining sheds in an orderly way, and blood vessels constrict to limit flow.
When ovulation doesn’t happen, progesterone never enters the picture. Estrogen keeps stimulating the lining to grow in a disorganized, fragile way. Eventually portions of it break down and slough off at random intervals. Without progesterone’s structural support, the usual mechanisms that control blood loss (vessel constriction, clot formation at the surface) don’t kick in properly. The result is often prolonged, heavy, or unpredictable bleeding.
Warning Signs of a Serious Problem
Certain patterns suggest you need evaluation sooner rather than later:
- Soaking through protection hourly: Flow heavy enough to saturate a pad or tampon every hour for several hours in a row can lead to significant blood loss and anemia.
- Periods longer than seven days: Prolonged bleeding increases your risk of iron deficiency and often signals an underlying cause that won’t resolve on its own.
- Passing large clots: While small clots can be normal during heavier flow days, repeatedly passing large clots suggests the body’s clotting mechanisms are overwhelmed by the volume of bleeding.
- Any postmenopausal bleeding: Even a single episode of spotting after 12 months without a period needs investigation.
- Bleeding after sex: This can point to cervical polyps, infections, or, less commonly, cervical changes that need evaluation.
Fatigue, dizziness, shortness of breath, or pale skin alongside heavy periods are signs of anemia from blood loss, which itself needs treatment even while the underlying cause is being sorted out.
How Abnormal Bleeding Is Diagnosed
The diagnostic process typically starts with a detailed history of your bleeding patterns, followed by blood work and imaging. A transvaginal ultrasound is usually the first imaging step, providing a view of the uterine lining and any structural abnormalities like fibroids or polyps.
If you’re at increased risk for endometrial problems (due to age, obesity, a history of irregular cycles, or certain other factors), an endometrial biopsy is often recommended. This involves taking a small tissue sample from the uterine lining, usually done in the office without anesthesia, though it can cause cramping. If ultrasound suggests a specific lesion but the biopsy doesn’t provide a clear answer, additional procedures like hysteroscopy (a thin camera inserted through the cervix) or a saline-infusion ultrasound can give a more detailed picture. MRI is sometimes used when other imaging is inconclusive.
For postmenopausal bleeding specifically, recent guidance from ACOG has shifted the approach. Previously, doctors often used ultrasound measurements of endometrial thickness alone to decide whether a biopsy was needed. Updated recommendations now favor combining ultrasound with tissue sampling for most patients from the start, because ultrasound thickness measurements alone missed too many cases of precancerous and cancerous changes. This means if you experience postmenopausal bleeding today, you’re more likely to get a biopsy during your initial workup than you would have a few years ago.
Treatment Depends on the Cause
Because abnormal bleeding has so many possible causes, treatment varies widely. Hormonal therapies (birth control pills, hormonal IUDs, or other hormone-based options) are often the first approach when the cause is ovulatory dysfunction or a hormonal imbalance. These work by providing the progesterone the body isn’t making on its own, stabilizing the lining and producing more predictable, lighter periods.
Structural problems like polyps or fibroids may need procedural removal if they’re causing significant symptoms. For people who have completed childbearing and haven’t responded to other treatments, more definitive surgical options exist. Infections causing bleeding are treated with targeted therapy for the specific organism involved.
When a clotting disorder turns out to be the underlying issue, which is particularly worth considering in teens with heavy periods from the start, treatment focuses on improving the body’s ability to control bleeding. Iron supplementation is commonly needed alongside any primary treatment, since chronic heavy bleeding depletes iron stores well before it shows up as full-blown anemia on routine blood work.