Heavy periods happen when the lining of your uterus builds up more than usual, your body has trouble stopping the bleeding efficiently, or both. Clinically, losing more than 80 milliliters of blood per cycle counts as heavy menstrual bleeding, but since no one measures that at home, a more practical benchmark is soaking through a pad or tampon every hour for several hours in a row. If that sounds familiar, there are several common reasons it happens and real options for reducing the flow.
How Hormones Control Your Flow
Your period is orchestrated by two hormones: estrogen and progesterone. During the first half of your cycle, estrogen thickens the uterine lining. After ovulation, progesterone stabilizes that lining and prepares it to shed in an orderly way if pregnancy doesn’t occur. When both hormones drop at the end of the cycle, you get your period.
Problems start when this balance tips. If you don’t ovulate in a given cycle, your body never produces the progesterone surge. Estrogen keeps building up the lining unopposed, and when it finally sheds, there’s simply more tissue and more blood to pass. This is one of the most common explanations for an unexpectedly heavy period, and it can happen to anyone occasionally. But certain conditions make skipped ovulation a pattern rather than a one-off.
Conditions That Cause Heavier Bleeding
Polycystic Ovary Syndrome (PCOS)
PCOS is a leading cause of irregular ovulation. Without regular ovulation, progesterone stays low and the uterine lining continues to thicken under estrogen’s influence. When a period finally arrives, it can be dramatically heavy. If your cycles are also irregular or spaced far apart, PCOS is worth investigating.
Uterine Fibroids and Polyps
Fibroids are noncancerous growths in or on the uterine wall. They increase the surface area of the lining and can interfere with the uterus’s ability to contract and clamp down on bleeding vessels after shedding. Polyps are smaller growths on the lining itself that bleed easily. Both are extremely common, particularly in your 30s and 40s, and are a frequent answer to “why did my period suddenly get heavier?”
Thyroid Problems
An underactive thyroid affects your period in two ways at once. First, low thyroid hormone disrupts ovulation, creating that same estrogen-dominant buildup in the lining. Second, hypothyroidism impairs your blood’s ability to clot normally. It can cause a form of platelet dysfunction similar to a genetic bleeding disorder called von Willebrand disease, meaning your body is slower to stop the bleeding once it starts. Even mildly low thyroid levels (subclinical hypothyroidism) can contribute.
Bleeding Disorders
Speaking of von Willebrand disease, it’s more common in women with heavy periods than most people realize. Among women with chronic heavy menstrual bleeding, somewhere between 5% and 24% turn out to have this condition. It’s often undiagnosed because heavy periods get normalized, but if you’ve bled heavily since your very first period, bruise easily, or have prolonged bleeding after dental work or minor cuts, a bleeding disorder could be the underlying cause.
Endometrial Hyperplasia
When the uterine lining thickens excessively over time without being shed regularly, the cells can crowd together and become abnormal. This is called endometrial hyperplasia, and it’s most common during perimenopause (when ovulation becomes erratic) and after menopause. Obesity also increases the risk, because fat tissue produces estrogen, adding to the hormonal imbalance. Hyperplasia causes heavy, prolonged bleeding and needs to be evaluated because some forms carry a small risk of progressing to uterine cancer.
Your IUD Could Be a Factor
If you have a copper IUD and your periods got noticeably heavier after insertion, that’s not a coincidence. Studies show copper IUDs increase menstrual blood loss by roughly 55 to 60% compared to pre-insertion levels. In one study, average blood loss went from 59 milliliters per cycle to 91 milliliters, pushing many women past the threshold for heavy bleeding. This increase tends to be most pronounced in the first several months but can persist.
Hormonal IUDs work in the opposite direction. The type that releases a small amount of progestin thins the uterine lining significantly, and users typically see their blood loss drop to around 20 milliliters per cycle. That’s one reason doctors sometimes recommend switching from a copper to a hormonal IUD when heavy bleeding becomes a problem.
Other Life Stages and Triggers
Perimenopause deserves special mention. In the years leading up to menopause, typically your 40s, ovulation becomes unpredictable. You might ovulate some months and not others, creating cycles where estrogen builds the lining for weeks before it finally breaks down. Periods during perimenopause can be shockingly heavy compared to what you experienced in your 20s and 30s, and this is the single most common time women search for answers about heavy bleeding.
Recent pregnancy changes also matter. A miscarriage, especially an incomplete one, can cause prolonged heavy bleeding. And in the months after giving birth, your first several periods may be heavier than your pre-pregnancy baseline as your hormones recalibrate.
How Heavy Bleeding Affects Your Body
The biggest health consequence of ongoing heavy periods is iron deficiency. Every period depletes your iron stores, and when you’re losing more blood than average, your body can’t replenish fast enough. Ferritin, the protein that stores iron, drops below 30 micrograms per liter in iron-deficient individuals. But symptoms show up well before your levels hit rock bottom: persistent fatigue, brain fog, feeling winded going up stairs, cold hands and feet, and cravings for ice or other non-food items.
Many women with heavy periods assume their exhaustion is just stress or poor sleep. If you’ve felt chronically drained and your periods are heavy, iron deficiency is the first thing to check. A simple blood test for ferritin and hemoglobin gives a clear answer.
What Actually Reduces the Bleeding
Anti-inflammatory pain relievers like ibuprofen and naproxen do more than ease cramps. They reduce menstrual blood loss by 20 to 46% on average when taken consistently during your period. These work by lowering levels of compounds called prostaglandins that promote both cramping and blood flow, so they’re a reasonable first step for periods that are heavy but not severe.
For heavier cases, a medication that helps blood clot more effectively can reduce bleeding by 40 to 65%. It’s taken only during the days of your period and works by stabilizing the clots your body forms naturally at the shedding sites in your uterine lining. In clinical trials, it worked even for women who had fibroids contributing to their bleeding.
Hormonal options are the most effective long-term approach. Birth control pills, hormonal IUDs, and other progestin-based treatments all thin the uterine lining, directly addressing the “too much lining” problem. A hormonal IUD is particularly effective because it delivers progestin right where it’s needed and can reduce blood loss by over 70%.
When structural problems like large fibroids or polyps are behind the bleeding, removing them often resolves it. This can range from a quick in-office procedure for polyps to minimally invasive surgery for fibroids, depending on their size and location.
Signs Your Bleeding Needs Evaluation
Not every heavy period means something is wrong. A single unusually heavy cycle can happen because you skipped ovulation that month, and your next period may return to normal. But certain patterns point to something worth investigating:
- Soaking through protection hourly for multiple consecutive hours
- Periods lasting longer than 7 days regularly
- Passing clots larger than a quarter
- Needing to change pads or tampons overnight to avoid leaking
- Symptoms of iron deficiency like persistent fatigue, dizziness, or shortness of breath
- A sudden change in your normal pattern, especially after age 40
Heavy periods are one of the most common gynecologic complaints, and they’re also one of the most treatable. The cause determines the best approach, so getting a clear diagnosis is the step that makes everything else easier.