Heavy periods have a wide range of causes, from hormonal shifts to underlying health conditions, and losing more than 80 mL of blood per cycle (roughly 16 soaked regular tampons over the entire period) crosses the clinical threshold for what doctors call heavy menstrual bleeding. A practical way to gauge it: if you’re soaking through a pad or tampon in less than two hours, passing clots the size of a quarter or larger, or bleeding for more than seven days, your flow qualifies as abnormally heavy. Here’s what could be behind it.
Hormonal Imbalance Is the Most Common Cause
Your uterine lining builds up each cycle under the influence of estrogen, and after ovulation, a second hormone called progesterone stabilizes that lining so it sheds in an orderly way. When you don’t ovulate during a given cycle, progesterone never kicks in. Estrogen keeps stimulating the lining unopposed, making it thicker and more fragile. When it finally breaks down, the shedding is heavier, longer, and less predictable than a normal period.
Skipped ovulation (called anovulation) can happen for many reasons. Polycystic ovary syndrome (PCOS) is one of the most common, but stress, rapid weight changes, thyroid problems, and even intense exercise can disrupt the hormonal chain reaction that triggers ovulation. The high estrogen levels left unchecked also weaken blood vessels in the uterine lining, increasing the total volume of blood lost.
Perimenopause and Age-Related Changes
If you’re in your 40s or even late 30s and your periods have become unpredictable, perimenopause is a likely explanation. During this transition, estrogen levels rise and fall erratically, and ovulation becomes inconsistent. Some cycles you may barely bleed; others may bring what’s sometimes called “flooding,” where you soak through protection in under an hour. These swings can last anywhere from a few years to a decade before periods stop entirely. The pattern of light-then-heavy cycles, skipped months, and shifting cycle lengths is characteristic of this stage.
Structural Problems in the Uterus
Fibroids and polyps are noncancerous growths that develop in or on the uterine wall. Fibroids are extremely common, especially in women over 30, and they increase the surface area of the lining that sheds each month. Polyps are smaller, finger-like growths on the inner lining that can bleed between periods or make periods heavier. Adenomyosis, a condition where the tissue that normally lines the uterus grows into the muscular wall, causes particularly painful, heavy periods and a feeling of pressure in the lower abdomen. All three conditions are detectable through imaging or a scope exam.
Medications That Increase Flow
Copper IUDs are a well-known culprit. Unlike hormonal IUDs, the copper version contains no hormones, and one of its most common side effects is heavier, more painful periods, particularly during the first few months after insertion. Blood thinners (anticoagulants) prescribed for heart conditions or clotting disorders also increase menstrual blood loss because they reduce your blood’s ability to clot normally. If your periods became noticeably heavier after starting a new medication, that connection is worth investigating.
Bleeding Disorders You May Not Know About
Von Willebrand disease is the most common inherited bleeding disorder in women, affecting roughly 1 in 100. But among women specifically evaluated for chronic heavy periods, the prevalence jumps to between 5% and 24%, according to the American College of Obstetricians and Gynecologists. Many women with the condition go years without a diagnosis, assuming their heavy periods are just normal for them. Clues that a bleeding disorder might be involved include heavy periods starting from your very first cycle, frequent nosebleeds, easy bruising, or prolonged bleeding after dental work or surgery.
How Heavy Bleeding Affects Your Body
The most immediate consequence of losing a lot of blood each month is iron deficiency. Your body uses iron to make hemoglobin, the protein in red blood cells that carries oxygen. When iron stores drop, you feel it: fatigue, brain fog, shortness of breath during exercise, cold hands and feet, and sometimes cravings for ice or other non-food items. Over time, low iron progresses to full anemia. The World Health Organization defines anemia in women as hemoglobin below 120 g/L, and women with heavy periods are roughly 3.5 times more likely to be anemic than those with normal flow.
Iron deficiency can exist even before anemia shows up on a standard blood count. Ferritin, a measure of your stored iron, drops first. A ferritin level below 15 μg/L signals depleted stores, and many women with heavy periods fall into this range without realizing it. If you’ve been told your blood count is “fine” but you still feel exhausted, asking specifically about ferritin can be revealing.
What Doctors Look For
Evaluation typically starts with a pelvic exam and blood work, including a complete blood count to check for anemia, thyroid function tests, and sometimes a pregnancy test. Depending on your age and symptoms, your doctor may order an ultrasound to look for fibroids, polyps, or other structural changes. A hysteroscopy, where a thin camera is inserted through the cervix to view the inside of the uterus directly, gives a more detailed picture. An endometrial biopsy, which removes a small sample of the uterine lining for examination under a microscope, is sometimes recommended for women over 35 or those with risk factors for endometrial abnormalities.
Options for Reducing Heavy Flow
Over-the-counter anti-inflammatory medications like ibuprofen and naproxen can reduce menstrual blood loss by about 25% to 30% when taken consistently during your period, not just when pain flares. They work by lowering the production of prostaglandins, chemicals that promote both cramping and heavier bleeding. For stronger results, a prescription medication called tranexamic acid helps blood clot more effectively in the uterus and improves symptoms in roughly 87% of women who use it, compared to about 61% with anti-inflammatories alone.
Hormonal treatments address the root cause in many cases. A hormonal IUD releases a small amount of progestin directly into the uterus, thinning the lining significantly. Many women using one see their periods become very light or stop altogether. Birth control pills, patches, and hormonal injections can also regulate cycles and reduce flow by providing the progesterone that anovulatory cycles lack. For structural problems like fibroids or polyps, procedures to remove the growths or, in more severe cases, to reduce or remove the uterine lining are options that your doctor would discuss based on whether future pregnancy is a consideration.
Signs You Need Urgent Care
Most heavy periods are manageable with medical guidance, but certain patterns signal that you should seek care quickly. Soaking through a pad or tampon every hour for several consecutive hours is one clear threshold. Passing clots the size of a quarter or larger, feeling dizzy or lightheaded, or having a racing heartbeat during your period are signs that blood loss is exceeding what your body can compensate for. Bleeding that appears suddenly and is far heavier than your usual pattern also warrants prompt evaluation, especially if you could be pregnant, since heavy bleeding in early pregnancy can indicate a miscarriage or ectopic pregnancy.