Dysfunctional uterine bleeding (DUB) is abnormal bleeding from the uterus that isn’t caused by a structural problem, pregnancy, or systemic disease. It’s most often the result of a hormonal imbalance that disrupts your normal menstrual cycle, particularly when your body fails to ovulate. The term itself has largely been replaced in medical practice by “abnormal uterine bleeding due to ovulatory dysfunction” (AUB-O), but many people and even some clinicians still use the older name. Regardless of the label, it describes the same core problem: your hormones aren’t cycling the way they should, and the lining of your uterus sheds unpredictably.
Why the Name Has Changed
For decades, “dysfunctional uterine bleeding” was a catch-all diagnosis given when no obvious physical cause for abnormal bleeding could be found. The problem was that it was vague and didn’t point toward a specific mechanism. In response, the International Federation of Gynecology and Obstetrics (FIGO) developed a classification system called PALM-COEIN, which sorts causes of abnormal uterine bleeding into nine categories. The first four (Polyp, Adenomyosis, Leiomyoma, Malignancy) are structural. The remaining five (Coagulopathy, Ovulatory dysfunction, Endometrial disorders, Iatrogenic causes, Not yet classified) are non-structural.
What used to be called DUB now falls primarily under the “O” category: ovulatory dysfunction. This matters because a more precise label helps guide treatment. If your doctor uses the term AUB-O, they’re talking about the same condition older sources call dysfunctional uterine bleeding.
How Hormonal Imbalance Causes the Bleeding
In a normal menstrual cycle, your ovaries release an egg (ovulation), which triggers a rise in progesterone. Progesterone stabilizes the uterine lining and then drops at a predictable time, causing the lining to shed evenly. That’s your period.
When ovulation doesn’t happen, progesterone never rises. Your ovaries still produce estrogen, though, and that estrogen continues stimulating the uterine lining to grow. Without progesterone to organize and limit that growth, the lining becomes thick, fragile, and uneven. It eventually breaks down in patches rather than shedding all at once, which is why the bleeding can be heavy, prolonged, or unpredictable.
There are two main patterns. In the more common one, one or more follicles persist in the ovary without releasing an egg, keeping estrogen levels elevated for an extended period. This creates what’s called “unopposed estrogen” stimulation, where the lining grows excessively and breaks down irregularly. In the less common pattern, the follicle fails early and estrogen drops quickly, triggering a premature, disorganized shedding of the lining.
What It Feels Like
The hallmark of this type of bleeding is irregularity. Your periods may come too frequently, too far apart, or at completely unpredictable intervals. When bleeding does occur, it can range from light spotting that lasts for weeks to sudden, very heavy flow. Some people experience both extremes in different cycles.
Heavy episodes can mean soaking through a pad or tampon every hour or two, passing large clots, or bleeding that lasts longer than seven days. Over time, this blood loss can lead to iron deficiency, which brings its own symptoms: fatigue, weakness, dizziness, pale skin, and difficulty concentrating. Many people don’t realize their exhaustion is connected to their bleeding until a blood test reveals low iron levels.
Who Is Most Affected
Anovulatory bleeding clusters at the two ends of reproductive life. Adolescents in the first few years after their first period are especially prone because their hormonal systems haven’t fully matured. Cycles without ovulation are common during this window and usually resolve on their own over time. On the other end, people approaching menopause experience increasingly erratic ovulation as their ovarian function declines, making irregular and heavy bleeding a frequent complaint in the years leading up to menopause.
Conditions that disrupt ovulation at any age can also trigger it. Polycystic ovary syndrome (PCOS) is one of the most common culprits. Thyroid disorders play a role too. Low thyroid function increases bleeding risk and can even cause an acquired form of von Willebrand syndrome, a blood clotting problem that makes heavy bleeding worse. Significant weight changes, chronic stress, and excessive exercise can all suppress ovulation as well.
How It’s Diagnosed
This is a diagnosis of exclusion, meaning your doctor needs to rule out structural and other causes before attributing the bleeding to ovulatory dysfunction. The first step is confirming you’re not pregnant, since pregnancy-related bleeding requires entirely different management.
From there, evaluation typically includes blood tests to check hormone levels, thyroid function, and blood clotting ability. If there’s concern about a structural problem (polyps, fibroids, or abnormal tissue growth), imaging comes next. Transvaginal ultrasound is usually the first-line tool. If the ultrasound doesn’t clearly show a normal uterine cavity, further evaluation with a procedure that allows direct visualization of the inside of the uterus or a saline-infused ultrasound may be needed.
For people with risk factors for precancerous changes in the uterine lining, such as older age, obesity, or a long history of irregular cycles, an endometrial biopsy is often recommended. This involves taking a small tissue sample from the lining to examine under a microscope. The concern is that years of unopposed estrogen can cause the lining to develop abnormal cell changes, so this step is important even though the biopsy itself is brief and typically done in the office.
First-Line Treatment: Hormonal Options
Since the root problem is a hormonal imbalance, the most common treatments work by restoring hormonal regulation of the uterine lining. Combined oral contraceptives (birth control pills containing both estrogen and a progestin) are frequently used because they impose a predictable hormonal cycle, thin the lining, and produce regular, lighter withdrawal bleeds. They work well for many people and have the added benefit of contraception.
A progestin-releasing intrauterine device (IUD) is another widely used option. It delivers a small amount of hormone directly to the uterine lining, which thins it significantly. Many users experience dramatically lighter periods, and some stop bleeding altogether. In a large Dutch trial comparing this type of IUD to a surgical procedure called endometrial ablation, both approaches produced major reductions in blood loss at two years. About 74% of IUD users reported satisfaction with their treatment. The IUD has the advantage of being reversible and less invasive, though 27% of users in that study eventually needed additional surgical treatment compared to 10% in the ablation group.
Cyclic progestin therapy, where you take a progestin for 10 to 14 days each month, is another approach. This mimics the progesterone your body would produce after ovulation, stabilizing the lining and triggering a predictable withdrawal bleed when you stop taking it.
Non-Hormonal and Surgical Options
For people who can’t or don’t want to use hormones, tranexamic acid is a non-hormonal medication that helps reduce heavy bleeding by preventing blood clots in the uterine lining from breaking down too quickly. The standard regimen is two tablets taken three times a day, only during the days of heavy bleeding, for a maximum of five consecutive days per cycle. It doesn’t regulate your cycle or address the underlying hormonal issue, but it can meaningfully reduce the volume of blood you lose.
When medications haven’t been effective or aren’t appropriate, surgical options exist. Endometrial ablation destroys the uterine lining to reduce or stop bleeding. It’s a relatively quick outpatient procedure, and satisfaction rates are high, around 84% at two years in the Dutch trial mentioned earlier. However, it’s only appropriate for people who are done having children, since it makes pregnancy unsafe. Some people who undergo ablation still experience bleeding that returns over time and may eventually need a hysterectomy.
Hysterectomy, the removal of the uterus, is the definitive treatment that permanently stops uterine bleeding. It’s reserved for cases where other treatments have failed or when there are additional concerns like precancerous changes in the lining.
When Heavy Bleeding Becomes Urgent
Most dysfunctional uterine bleeding is manageable and not immediately dangerous, but heavy episodes can occasionally become acute. If you’re soaking through a pad or tampon every hour for several consecutive hours, feeling lightheaded or faint, or passing very large clots, that level of blood loss may need prompt medical attention to prevent complications. Chronic heavy bleeding that goes untreated for months or years can lead to significant iron deficiency anemia, which affects your energy, cognitive function, and heart health. If your periods have been consistently heavy and you’re experiencing fatigue or shortness of breath with normal activity, a simple blood count can determine whether you’ve become anemic.