Heavy periods are one of the most common gynecological complaints, and they almost always have an identifiable cause. A normal period lasts about four to five days and produces two to three tablespoons of blood total. If your flow soaks through a pad or tampon every hour for several hours in a row, lasts longer than seven days, or regularly includes large clots, something specific is driving that excess bleeding.
The causes range from hormonal shifts to structural changes in the uterus to underlying medical conditions you may not know you have. Understanding which category your heavy bleeding falls into is the first step toward getting it under control.
Hormonal Imbalance Is the Most Common Cause
Your menstrual cycle depends on a precise back-and-forth between two hormones: estrogen and progesterone. During the first half of your cycle, estrogen thickens the uterine lining to prepare for a potential pregnancy. After ovulation, progesterone rises and stabilizes that lining. When progesterone drops at the end of the cycle, the lining sheds in an orderly way, producing your period.
Problems start when ovulation doesn’t happen. Without ovulation, your body never produces that surge of progesterone, so estrogen keeps building the lining unopposed, month after month. The lining grows thicker than it should, and when it finally sheds, the result is a heavier, longer, and less predictable period. This pattern, called anovulation, is especially common during puberty, the years leading up to menopause, and in people with polycystic ovary syndrome (PCOS).
Thyroid problems can trigger the same cascade through a different route. Low thyroid hormone suppresses the signals your brain sends to your ovaries, disrupting ovulation. It also changes how your blood clots, which can make bleeding heavier on its own. And it can cause the uterine lining to thicken unpredictably. If your heavy periods came on gradually alongside fatigue, weight changes, or feeling cold all the time, an underactive thyroid is worth investigating.
Structural Changes in the Uterus
Sometimes the uterus itself has changed in a way that produces more bleeding. Doctors organize these structural causes using a framework called PALM: polyps, adenomyosis, leiomyomas (fibroids), and malignancy or hyperplasia. Each one affects bleeding differently.
Fibroids and Polyps
Fibroids are noncancerous growths in the muscular wall of the uterus. They’re extremely common, particularly after age 30, and their effect on bleeding depends largely on location. A fibroid pressing into the uterine cavity distorts the lining and increases the surface area that bleeds each month. Polyps are smaller, finger-like growths on the lining itself. Both can cause periods that are heavier than usual and may also produce bleeding between periods.
Adenomyosis
Adenomyosis happens when tissue that normally lines the uterus grows into the muscular wall instead. This causes the uterus to enlarge and thicken. During your period, that embedded tissue bleeds inside the muscle, producing heavy flow, large clots, and significant cramping. Unlike endometriosis, which causes pain primarily during menstruation, adenomyosis can cause a dull ache or pressure even between periods. It’s a leading cause of heavy bleeding in women in their 30s and 40s, and it often goes undiagnosed for years because ultrasound findings can be subtle.
Endometrial Hyperplasia
When the uterine lining keeps growing without the monthly reset that progesterone provides, the cells can crowd together and become abnormal. This is called endometrial hyperplasia, and it produces irregular, heavy bleeding. Left untreated, some forms carry a risk of progressing to uterine cancer, which is why persistent heavy bleeding in someone over 40 (or younger, with risk factors) typically prompts a biopsy of the lining.
Bleeding Disorders You Might Not Know About
Between 5% and 24% of women with chronic heavy periods have an undiagnosed bleeding disorder, most commonly von Willebrand disease. This is an inherited condition where your blood doesn’t clot efficiently. It’s significantly underdiagnosed because many people assume their heavy periods are just “normal for them.” The prevalence varies by ethnicity: roughly 16% among white women with heavy bleeding compared to about 1% among Black women with the same symptoms.
Clues that a bleeding disorder might be involved include heavy periods that started with your very first cycle in adolescence, a history of easy bruising, prolonged bleeding after dental work or surgery, or a family member with similar issues. If that profile sounds familiar, specific blood tests can identify or rule out the condition.
Medications That Increase Flow
Certain medications make periods heavier as a side effect. Blood thinners are the most obvious culprit, but copper IUDs (the non-hormonal type) commonly increase menstrual flow, especially in the first several months after insertion. Anti-inflammatory drugs like aspirin also reduce clotting and can tip a borderline-heavy period into a genuinely problematic one. If your periods changed after starting a new medication, that connection is worth raising with your doctor.
How Heavy Bleeding Affects Your Body
The most immediate consequence of months or years of heavy periods is iron deficiency anemia. Every period depletes your iron stores, and if you’re losing more blood than your body can replace, those stores eventually bottom out. The symptoms creep up gradually: persistent fatigue that sleep doesn’t fix, feeling short of breath climbing stairs, dizziness when you stand up quickly, difficulty concentrating, and looking noticeably pale. Many people chalk these symptoms up to stress or poor sleep without realizing their period is the root cause.
A simple blood test measuring ferritin (your stored iron) and hemoglobin can confirm anemia. If your periods are heavy and you’re experiencing any of those symptoms, getting your iron levels checked is one of the most useful things you can do.
Treatment Options That Reduce Flow
Treatment depends on the cause, but several options can dramatically reduce bleeding regardless of the underlying reason.
Hormonal IUD
A hormonal IUD releases a small amount of progesterone directly into the uterus, thinning the lining and reducing flow substantially. In clinical trials, women using a hormonal IUD saw their bleeding scores drop from roughly 616 to 65 on a standardized scale over two years. About 27% of users eventually needed a surgical procedure for additional management, compared to 10% of women who went straight to surgery, but for many people the IUD provides enough relief on its own and avoids an operation entirely.
Non-Hormonal Medication
If you prefer to avoid hormones, tranexamic acid is a pill that works by preventing blood clots from breaking down too quickly. You take it only during your period (up to five days per cycle), and it reduces flow without affecting your hormones or fertility. It won’t treat an underlying cause like fibroids, but it can make heavy periods significantly more manageable while you and your doctor figure out next steps.
Endometrial Ablation
For people who are done having children, endometrial ablation destroys the uterine lining using heat, radiofrequency energy, or other methods. About 50% of women who have the procedure stop getting periods altogether, and satisfaction rates range from 80% to 96%. Reintervention rates sit around 10%. It’s a relatively quick outpatient procedure, but it’s not reversible, and pregnancy after ablation is dangerous, so reliable contraception is still necessary if you haven’t had a tubal ligation or your partner hasn’t had a vasectomy.
Hormonal Birth Control
Combination birth control pills, the hormonal patch, and the hormonal ring all thin the uterine lining by providing steady progesterone. They’re often the first thing prescribed for heavy periods in younger people, and they’re effective for hormonal causes in particular. Progesterone-only pills can work similarly but are less predictable in controlling bleeding patterns.
What to Pay Attention To
Not every heavy period needs an urgent workup, but certain patterns signal that something beyond a one-off hormonal fluctuation is going on. Periods that have gotten progressively heavier over several months, bleeding that consistently lasts more than seven days, needing to change protection every one to two hours, passing clots larger than a quarter, or developing symptoms of anemia all warrant investigation. The same is true if heavy bleeding is new for you after years of lighter periods, since a change in your baseline pattern is more significant than a flow that’s always been on the heavier side.
Diagnosis usually involves blood work to check for anemia, thyroid function, and clotting disorders, along with an ultrasound to look for fibroids, polyps, or adenomyosis. In some cases, a closer look at the uterine lining through a saline-infusion ultrasound or hysteroscopy provides more detail. The cause is identifiable in the vast majority of cases, and nearly all of them are treatable.