Heavy periods have several possible causes, ranging from hormonal imbalances to structural growths in the uterus to underlying blood disorders. In many cases, the cause is treatable once identified. Understanding what’s behind the heavy bleeding is the first step toward getting it under control.
How to Tell if Your Period Is Actually Heavy
Most people have a general sense that their period is heavier than normal, but there are some practical signs worth paying attention to. You likely have heavy menstrual bleeding if you soak through a pad or tampon every hour for several consecutive hours, need to use double protection (a pad and a tampon at the same time), wake up at night to change protection, pass blood clots larger than a quarter, or bleed for more than seven days. Persistent heavy periods also put you at risk for iron deficiency anemia, which can cause fatigue, weakness, and shortness of breath. Iron deficiency accounts for roughly 75% of all anemia cases in reproductive-aged women, and heavy menstrual bleeding is a major contributor.
Hormonal Imbalance
The most common cause of heavy periods is a hormonal imbalance between estrogen and progesterone. During a normal cycle, estrogen thickens the uterine lining in the first half, preparing for a potential pregnancy. After ovulation, progesterone rises and stabilizes that lining. If pregnancy doesn’t happen, both hormones drop, and the lining sheds in a controlled way as your period.
When ovulation doesn’t occur, progesterone is never produced. Without progesterone to keep it in check, estrogen continues stimulating the uterine lining, causing it to grow thicker than normal. When this overgrown lining finally sheds, the result is heavier, longer bleeding. This condition is called endometrial hyperplasia, and it’s especially common during times when ovulation is irregular: the first few years of menstruation, the years leading up to menopause, and in conditions like polycystic ovary syndrome (PCOS) where ovulation is frequently skipped.
Uterine Fibroids
Fibroids are benign growths made of smooth muscle that develop in or on the uterus. They’re extremely common, and many people who have them experience no symptoms at all. But fibroids that grow into the uterine cavity or distort the uterine wall can significantly increase menstrual bleeding. Their location matters more than their size. A small fibroid pressing into the lining of the uterus can cause heavier periods than a large one growing on the outer surface. Fibroids are sensitive to hormones and tend to grow during the reproductive years, often shrinking after menopause.
Uterine Polyps
Polyps are soft, finger-like growths that attach to the inner wall of the uterus. They form when cells in the uterine lining overgrow, and like fibroids, they’re estrogen-sensitive, meaning they grow in response to estrogen circulating in the body. Polyps can cause heavy menstrual flow, bleeding between periods, and irregular cycles. They range in size from a few millimeters to several centimeters and can sometimes be removed during a simple office procedure.
Adenomyosis
Adenomyosis occurs when tissue from the uterine lining grows into the muscular wall of the uterus itself. This makes the uterus thicker, more enlarged, and more tender. Each month, the misplaced tissue still responds to hormonal signals, swelling and bleeding within the muscle. The result is often heavy, prolonged periods along with significant cramping. Adenomyosis is sometimes confused with fibroids because both enlarge the uterus, but they’re distinct conditions. It’s most commonly diagnosed in women in their 30s and 40s.
Thyroid Problems
An underactive thyroid (hypothyroidism) can cause heavy periods through a chain reaction of hormonal disruption. Low thyroid hormone suppresses the signals your brain sends to your ovaries, interfering with normal ovulation. It also raises levels of prolactin, a hormone that affects estrogen production. On top of that, insufficient thyroid hormone can change how your blood clots, potentially leading to heavier bleeding. The uterine lining may thicken excessively and shed unpredictably. Thyroid issues are a commonly overlooked cause of heavy periods, and a simple blood test can identify them.
Bleeding Disorders
Some people bleed heavily during their periods because their blood doesn’t clot properly. The most common inherited bleeding disorder in women is von Willebrand disease, which affects the blood’s ability to form clots efficiently. Among women with chronic heavy menstrual bleeding, somewhere between 5% and 24% are found to have von Willebrand disease. The prevalence varies by ethnicity: roughly 16% among Caucasian women with heavy bleeding compared to about 1% among African American women.
Bleeding disorders are worth considering if you’ve had heavy periods since your very first cycle, bruise easily, bleed excessively after dental work or surgery, or have a family history of bleeding problems. These conditions are often undiagnosed for years because heavy periods are frequently dismissed as normal.
Other Contributing Factors
Copper intrauterine devices (IUDs) are a well-known cause of heavier periods, particularly in the first several months after insertion. Certain medications that thin the blood or affect clotting can also increase menstrual flow. Less commonly, heavy bleeding can be a sign of uterine or cervical cancer, particularly in women over 40 or those with irregular bleeding patterns that don’t respond to initial treatment. Endometrial biopsy is typically used to rule this out.
How the Cause Is Identified
Finding the reason behind heavy periods usually involves a combination of blood tests and imaging. Blood work checks for anemia, thyroid function, and clotting disorders. An ultrasound uses sound waves to create images of the uterus and ovaries, revealing fibroids, polyps, or other structural changes. If more detail is needed, a sonohysterography (where fluid is injected into the uterus before ultrasound) can highlight abnormalities in the uterine lining more clearly.
For a direct look inside the uterus, a hysteroscopy involves inserting a thin, lighted camera through the cervix. An endometrial biopsy, where a small tissue sample is taken from the uterine lining, helps check for hyperplasia or precancerous changes. The specific tests your provider recommends will depend on your age, symptoms, and risk factors.
Treatment Options Based on the Cause
Treatment depends entirely on what’s causing the heavy bleeding. Hormonal imbalances are often managed with hormonal birth control or other hormone-based therapies that regulate the cycle and thin the uterine lining. For fibroids or polyps, removal procedures can resolve the problem, sometimes without major surgery.
For heavy bleeding without a clear structural cause, medications that help blood clot more effectively can reduce flow by 40% to 65% within a few cycles. Anti-inflammatory medications also help, though they tend to be somewhat less effective, reducing bleeding by a smaller margin. These are typically taken only during the days of your period, not continuously.
When the cause is a thyroid disorder or bleeding condition like von Willebrand disease, treating the underlying condition often improves periods significantly. For adenomyosis that doesn’t respond to other treatments, more involved procedures may be considered. The important thing is that heavy periods are not something you simply have to live with. Nearly every cause has an effective treatment once it’s properly identified.