Heavy periods have a range of causes, from hormonal shifts to structural changes in the uterus to underlying health conditions. If you’re soaking through a pad or tampon in less than two hours, passing blood clots the size of a quarter or larger, or bleeding for more than seven days, your period qualifies as heavy by medical standards. Understanding what’s behind it can help you figure out what to do next.
How to Tell If Your Period Is Actually Heavy
It’s easy to assume everyone bleeds the same amount, so many people with genuinely heavy periods don’t realize theirs are outside the norm. The CDC considers a period heavy if you need to change your tampon or pad after less than two hours, or if your flow soaks through one or more pads or tampons every hour for several hours in a row. Blood clots the size of a quarter or bigger are another clear sign.
Other practical clues: needing to double up on pads, waking up at night to change protection, or routinely bleeding through clothing or bedding. If any of these sound familiar, something is driving the excess bleeding, and it’s worth figuring out what.
Hormonal Imbalance Is the Most Common Cause
Your menstrual cycle depends on a 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 possible pregnancy. After ovulation, progesterone rises and stabilizes that lining. If pregnancy doesn’t happen, both hormones drop, and the lining sheds as your period.
The problem starts when you don’t ovulate. Without ovulation, progesterone never kicks in, and estrogen keeps building up the uterine lining unopposed. The lining grows thicker than it should, and when it finally sheds, the result is a heavier, longer, and often unpredictable period. This pattern is especially common during puberty, perimenopause, and in people with polycystic ovary syndrome (PCOS), all situations where irregular ovulation is the norm.
Fibroids and Adenomyosis
Uterine fibroids are noncancerous growths in or on the wall of the uterus. They’re extremely common, particularly after age 30, and the ones that grow closest to the inner lining tend to cause the heaviest bleeding. They can distort the shape of the uterine cavity, increase its surface area, and make periods significantly worse.
Adenomyosis is a related but different condition. It happens when the tissue that normally lines the uterus starts growing into the muscular wall. This increases both the surface area and the blood supply of the lining, which directly leads to heavier flow. Between 40% and 60% of people with adenomyosis experience heavy menstrual bleeding. It’s distinct from endometriosis, where similar tissue grows outside the uterus, though the two conditions often occur together. Adenomyosis can be tricky to diagnose because on an ultrasound, focal patches of it can look like small fibroids. MRI is better at telling the two apart.
Bleeding Disorders You Might Not Know About
Some people bleed heavily because their blood doesn’t clot as efficiently as it should. Von Willebrand disease is the most common inherited bleeding disorder, and it’s significantly underdiagnosed in women. Among those with chronic heavy periods that have no other obvious explanation, somewhere between 5% and 24% turn out to have Von Willebrand disease. That’s a surprisingly high number, and it means a bleeding disorder is worth investigating if your heavy periods started at your very first cycle and no one has found another cause.
Signs that a bleeding disorder might be involved include easy bruising, prolonged bleeding after dental work or minor cuts, and a family history of heavy bleeding. A simple blood test can screen for it.
Thyroid Problems and Other Medical Conditions
An underactive thyroid (hypothyroidism) can make your periods heavier through several mechanisms. Low thyroid hormone alters the way your blood clots, potentially increasing menstrual flow. It can also disrupt ovulation, leading to the same estrogen-dominant pattern described above. Thyroid disorders are common and easy to test for, which is why checking thyroid function is often one of the first steps when someone reports heavy periods.
Other systemic conditions that can contribute include liver disease, kidney disease, and certain medications that affect clotting, like blood thinners.
Your IUD or Medication Could Be a Factor
If your heavy periods started after getting a copper IUD, that’s likely the connection. Copper IUDs are known to increase menstrual bleeding and cramping, especially in the first several months. This tends to improve over time, but for some people it doesn’t ease up enough to be tolerable.
Hormonal IUDs work in the opposite direction. They typically lighten periods dramatically, and some people stop bleeding altogether while using one. If you switched from a hormonal IUD or hormonal birth control to a non-hormonal method (or stopped contraception entirely), what feels like suddenly heavier periods may actually be a return to your body’s natural, unmedicated flow.
Blood-thinning medications and even regular use of certain over-the-counter pain relievers that affect clotting can also increase menstrual bleeding.
What Heavy Periods Do to Your Body Over Time
The biggest downstream risk of chronically heavy periods is iron deficiency anemia. Every period depletes your iron stores, and when you’re losing more blood than average each month, your body may not be able to keep up. Symptoms of iron deficiency include fatigue that doesn’t improve with rest, brain fog, shortness of breath during mild activity, pale skin, and brittle nails. Many people with heavy periods have been living with low iron for so long they’ve adjusted to feeling tired and assume it’s normal. A blood test checking your iron levels and hemoglobin can confirm whether anemia is part of the picture.
How Heavy Periods Are Treated
Treatment depends entirely on what’s causing the problem, which is why getting to the root matters more than just managing symptoms.
For hormonally driven heavy bleeding, the most common first step is some form of hormonal management. A hormonal IUD is one of the most effective options because it delivers a small amount of hormone directly to the uterine lining, thinning it significantly and reducing flow. Oral contraceptives can also regulate the cycle and prevent the lining from building up excessively. For people who don’t want hormonal treatment, certain prescription medications can reduce bleeding during your period by helping the blood clot more effectively at the uterine lining.
Fibroids and adenomyosis may respond to hormonal treatments, but depending on their size and severity, they sometimes require procedures. Options range from minimally invasive techniques that target fibroids specifically to, in more severe cases, surgery. The right approach depends on the size and location of growths, how much they’re affecting your life, and whether you want to preserve fertility.
If a bleeding disorder like Von Willebrand disease is the cause, targeted treatment exists to improve clotting during your period. And if hypothyroidism is behind it, treating the thyroid issue with medication often brings periods back to a normal flow on its own.
Whatever the cause, if you’ve been bleeding through pads in under two hours, passing large clots, or dealing with periods that drag past a week, this is a solvable problem. Tracking your cycle and flow patterns before your appointment gives your provider a clearer starting point for figuring out what’s going on.