Why Is My Period So Heavy? 10 Possible Causes of Heavy Periods

Written by the MyOvly Editorial Team. Medically verified against current guidance from the NHS, Mayo Clinic, Johns Hopkins Medicine, Cleveland Clinic, the CDC and MedlinePlus. Last updated for MyOvly readers.

Soaking through a pad in under an hour, changing your tampon in the middle of the night, or noticing clots the size of a coin can make you wonder if what you’re experiencing is even still normal. Heavy periods in women are common, and periods vary a lot from person to person, which makes it genuinely hard to know where ordinary heavy flow ends and something worth mentioning to a doctor begins.

This guide walks through what actually counts as a heavy period, the hormonal and structural reasons it happens, and when heavy bleeding is a reasonable thing to bring up with a healthcare professional rather than just live with.

Why Is My Period So Heavy?

Understanding your menstrual cycle phases helps explain why bleeding happens at all. Each month, hormones build up the lining of your uterus, called the endometrium, in preparation for a possible pregnancy. If pregnancy doesn’t happen, that lining sheds, and that’s your period.

Heavy periods, sometimes called menorrhagia, heavy menstrual bleeding, or more broadly abnormal uterine bleeding, happen when that shedding involves more menstrual blood loss than is typical, a heavier than usual menstrual flow, prolonged menstrual bleeding, or both. According to the NHS, heavy periods are common, and for some people a heavy flow may simply be normal for their body rather than a sign of a problem. Sometimes bleeding is heavier at certain life stages too, such as when periods first start, after pregnancy, or as you approach menopause, reflecting ordinary hormonal changes rather than a specific condition.

There isn’t one single cause of heavy periods. It can come down to a hormone imbalance, a structural issue in the uterus, an underlying medical condition, or in some cases no clear cause at all. Since this touches on both reproductive health and overall women’s health, the rest of this guide walks through the most common explanations.

What Counts as a Heavy Period?

Because there’s no easy way to measure blood loss at home, doctors generally rely on how bleeding affects your daily life rather than an exact volume, along with other period symptoms you might be noticing alongside the flow itself, such as period cramps or fatigue.

According to Mayo Clinic, signs that point toward excessive menstrual bleeding include soaking through one or more pads or tampons every hour for several hours in a row, needing to use double protection to manage your flow, waking up at night specifically to change your period product, menstrual bleeding lasting more than seven days, and passing large blood clots, sometimes called menstrual clots, larger than a quarter.

If several of these apply to you regularly, that pattern of abnormal menstrual bleeding, or an unusually heavy period that keeps repeating, is worth discussing with a healthcare provider, even if you’ve simply assumed it’s just how your body works.

Hormonal Causes of Heavy Periods

A hormone imbalance is one of the most common reasons behind heavy bleeding, and it often comes down to the relationship between estrogen and progesterone.

According to Johns Hopkins Medicine, hormone problems or conditions that affect the uterus can result in heavy bleeding, and this is one of the two broad categories doctors usually consider first. When estrogen and progesterone are out of balance, the uterine lining can build up thicker than usual, so a thickened uterine lining simply means there’s more of it to shed once your period starts.

This kind of hormonal change often shows up around specific menstrual cycle changes and transitions. It’s common during puberty, when cycles haven’t yet settled into a regular pattern and irregular periods with ovulation problems are typical, and again during perimenopause, as hormone production becomes less predictable. If you’ve noticed heavier bleeding during a particular part of your cycle, our guide to the follicular phase after your period explains how rising estrogen in that stage affects the uterine lining in the first place, which is part of what sets the stage for how heavy the next period will be.

Uterine Conditions That Cause Heavy Bleeding

Beyond hormones, several common, usually noncancerous conditions affecting the structure of the uterus can lead to heavier or longer periods.

Uterine fibroids. According to MedlinePlus, fibroids are common noncancerous growths in the uterus, affecting as many as one in five people during their reproductive years, and common symptoms include a heavy period with clots and periods that last longer than usual. A heavy period and blood clots together, especially larger ones, are one of the more recognizable signs fibroids may be involved.

Polyps. These are small, benign growths on the lining of the uterus, known medically as uterine polyps. They can cause heavy or prolonged bleeding, and sometimes bleeding between periods as well.

Adenomyosis. In this condition, tissue similar to the uterine lining grows into the muscular wall of the uterus itself. This is one of the more common explanations behind heavy periods and cramps together, since it can lead to both heavier bleeding and more painful periods than you’re used to.

Endometriosis. Similar tissue can also grow outside the uterus entirely, which is linked to heavy periods and pain for some people, extending beyond just the days you’re bleeding.

None of these conditions are rare, and having one doesn’t necessarily mean something is seriously wrong. Many people live with fibroids or polyps without symptoms at all, discovered only incidentally during an unrelated exam. The point of knowing about them is simply to recognize that persistent heavy bleeding often has an identifiable, manageable cause, and that a doctor’s evaluation is generally about narrowing that down rather than something to dread.

Other Medical Causes Behind Heavy Bleeding

A handful of other causes are worth knowing about, since they don’t always come up in a quick internet search but are genuinely common.

PCOS and ovulation related changes. When ovulation doesn’t happen regularly, as can occur with polycystic ovary syndrome, the uterine lining can build up for longer stretches between periods, which sometimes results in a heavier bleed when it finally does shed. This same irregular ovulation pattern is often part of why a period arrives unpredictably in the first place. If your cycles feel unpredictable in timing as well as flow, our guide on why your period might be late covers many of the same underlying hormonal patterns from a different angle.

Copper IUDs. Heavy menstrual bleeding is a well documented side effect of the hormone free copper intrauterine device, particularly in the first several months after it’s placed. Switching to a hormonal contraception method, or another form of birth control entirely, is something to discuss with your provider if the bleeding doesn’t ease over time.

Pregnancy related causes. A single unusually heavy, late period can sometimes be related to an early pregnancy loss. Heavy bleeding alongside severe cramping and other pregnancy complications is a reasonable prompt to seek medical attention rather than wait it out.

Bleeding disorders. According to the CDC, women are more likely than men to notice symptoms of von Willebrand disease, the most common inherited blood clotting disorder, largely because of the bleeding challenges involved in menstruation. Heavy periods with large clots that started right from your very first period, and never really improved, are the first real clue for some people that something clotting related is going on, and the CDC notes it can take an average of years for that connection to be made.

Thyroid problems and other illness. An underactive thyroid, along with certain liver or kidney conditions, can also disrupt the hormonal balance involved in regulating your period.

Certain medications. Blood thinners in particular are a well known cause of heavier than usual bleeding, since they work by affecting how easily your blood clots.

Tracking Heavy Periods and Easing Symptoms

Noticing a pattern over several cycles, rather than judging any single period in isolation, tends to give you and your doctor far more useful information than a one off description of “it’s really heavy.”

Keeping a simple record of how many pads or tampons you use per day, how many days your period lasts, and whether you’re passing large clots can help you spot whether a particular cycle was unusually heavy for you specifically, or whether a heavy period every month has simply become your normal pattern. Some people also notice other symptoms clustering around heavy bleeding during their period, including stronger cravings; our piece on period cravings explains what’s actually behind that pattern, separate from bleeding itself. Fatigue is also worth watching for, since heavy blood loss over time can lead to iron deficiency anemia, which often shows up as tiredness or shortness of breath. If weight changes tend to show up around the same time each month too, our guide to luteal phase weight gain covers a separate but related hormonal pattern that some people notice alongside heavier premenstrual symptoms.

Simple measures like taking an anti inflammatory pain reliever as directed, staying hydrated, and eating iron rich foods during a heavy cycle can help with day to day comfort, though they don’t address an underlying cause if one exists.

When Should You See a Doctor About Heavy Periods?

Heavy periods don’t always need treatment, but there are clear situations where it’s worth having a conversation with a healthcare professional rather than assuming it will resolve on its own.

According to the NHS, it’s worth seeing a GP if heavy periods are affecting your daily life, if you’ve had heavy periods for some time without them improving, if you experience severe pain during your period, if you bleed between periods or after sex, or if heavy bleeding comes with other symptoms such as pain when using the bathroom or during sex.

Cleveland Clinic adds that heavy bleeding severe enough to soak through protection every hour for several consecutive hours, or bleeding accompanied by symptoms of anemia like fatigue and shortness of breath, is worth a medical evaluation rather than waiting to see if it improves on its own.

A doctor evaluating heavy periods will usually start with your history and a pelvic examination, and may follow up with blood tests to check for anemia or a clotting problem, or imaging such as an ultrasound to look for fibroids or polyps. None of this means something serious is automatically wrong. It’s simply the process of narrowing down which of the causes above, if any, applies to you specifically, so that treatment can actually target the real reason rather than guessing.

Quick Answers to Common Questions

Conclusion

A heavy period is common, and for some people it genuinely is just what’s normal for their body. But when bleeding regularly interferes with daily life, lasts longer than a week, or comes with clots, fatigue, or pain that feels disproportionate, that pattern deserves a proper look rather than quiet endurance. The causes range from ordinary hormonal shifts to fibroids, polyps, thyroid issues, or, less commonly, a bleeding disorder, and most of them are manageable once identified.

Tracking your own pattern over a few cycles, through MyOvly or another method you trust, is one of the most useful things you can bring into that conversation with a healthcare professional, since it turns a vague sense of “this feels like a lot” into something concrete they can actually work with.

Medical disclaimer: This article is for general educational purposes and is not a substitute for personalized medical advice. If you have concerns about heavy or unusual menstrual bleeding, speak with a qualified healthcare professional.