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The dangers of heavy menstrual bleeding
25th July, 2026 07:15 PM
Heavy menstrual bleeding is a serious health condition. Only now are we starting to understand what causes it – and how it can be treated.
From the age of 12-13 onwards, Michelle Alston slept off the worst days of her menstrual periods in the school nurse’s office, battling severe pain as she bled through period products. “I was taught that this is just normal,” she says. “This is just something that you have to learn to cope with.”
She felt weak, failing to cope with her periods as well as her peers seemed to. It wasn’t until she reached her early 40s that she learnt weakness had little to do with it – her periods were unusually heavy.
When bleeding during periods is so extensive that it interferes with quality of life, doctors call it heavy menstrual bleeding, and it’s a serious medical problem.
Studies of populations from around the world estimate that between 10 and 30% of reproductive-aged women experience heavy menstrual bleeding like Alston’s. And due to under-reporting and a general lack of understanding of how much bleeding is too much, studies suggest it may actually occur in half of all reproductive-aged women.
Heavy menstrual bleeding can also signify other health problems and have serious consequences when unchecked, such as anaemia.
Yet, only recently have researchers begun exploring the resulting harms from heavy menstrual bleeding in depth, pursuing better diagnostics and treatments. A search of PubMed (a database of biomedical research publications) for the term “menstrual blood” yielded just 400 publications in the last decade. Publications for “semen”, for instance, number over 15,000.
“Women are probably owed years, if not decades, of research,” says Jackie Maybin, a gynaecologist at the University of Edinburgh in Scotland and programme director of The Missed Vital Sign, a research initiative for heavy menstrual bleeding. “And I think the time is now.”
How much blood is too much?
For researchers, heavy menstrual bleeding is blood loss of over 80ml per cycle, blood clots exceeding the size of a US quarter, or periods lasting beyond seven days. But for those of us who menstruate, there’s no standardised or metric conversion for the practical ways of measuring bleeding: the number of bathroom visits, pads or tampons changed, or bloodstained pairs of underwear.
Some clinicians try to meet patients halfway, asking them to judge their blood loss using charts featuring progressively bloodier pads and tampons. But that too is imprecise, as all period products aren’t created equal and often vary widely in absorption.
As a result, determining how much blood is too much during a period isn’t straightforward, and often clinicians have to determine heavy menstrual bleeding by whether it interferes with quality of life.
“The patient sometimes doesn’t realise that the amount of bleeding they’re having is not normal, and that actually, something can be done about it,” says Adwoa Christy, a clinical professor in the department of gynaecology, obstetrics, and reproductive sciences at the University of California, San Francisco.
Alston routinely bled through her sheets and clothes, and once, onto an unforgivingly white chair at a mobile phone shop. She just thought she was doing something wrong, and maybe that she needed different period products to contain the flow.
She was told to accept that experiencing painful cramps and embarrassing bloodstains while on your period is normal. In other regions of the world, period taboos and stigma run deeper.
“I think there are a lot of people in my part of the world who may not complain about it, and who, maybe because of normalisation [of pain] and stigma, don’t actually come to a doctor,” says Hemantha Senanayake, emeritus professor of obstetrics and gynaecology at the University of Colombo in Sri Lanka and head of the Asian Society of Endometriosis and Adenomyosis (both conditions that can cause heavy menstrual bleeding).
And while gynaecologists may know to ask detailed questions to detect heavy menstrual bleeding, clinicians outside the field may overlook the signs. Alston waited nearly 30 years before someone identified her heavy menstrual bleeding, and she’s far from alone.
Heavy menstrual bleeding is not just a symptom
While a problem in its own right, heavy menstrual bleeding is primarily a symptom of a larger issue. It arises from a variety of conditions, including polyps, fibroids, cancer, blood disorders, ovulatory issues, and endometrial disorders, such as endometriosis.
It is also common – though still something to address – when someone first starts having periods and during the transition to menopause, when the body’s hormonal choreography is in a period of transition.
Treating these conditions can lessen the heavy bleeding, but scientists still don’t know how these conditions interfere with the quantity of blood loss, exactly. “There’s been a lot of research focusing on the fibroids themselves, but not why they cause the heavy bleeding, for example,” says Maybin, who notes that fibroids are noncancerous growths in uterine muscle.
On the other hand, forgoing treatment for heavy menstrual bleeding can create new problems, such as iron deficiency. Iron is an essential mineral for maintaining healthy cells, immune systems, muscles, skin, hair and nails. Brain fog, dizziness, shortness of breath, easy bruising and hair loss can all set in when iron levels begin to flag.
In this way, the harms of heavy menstrual bleeding persist even outside of menstrual periods: studies estimate that over 40% of women with heavy menstrual bleeding also have iron deficiency.
Alston found herself in those statistics too: she was always cold and often craved eating ice cubes, a bizarre but telling clue of iron deficiency that’s still poorly understood by researchers.
If unaddressed, iron deficiency can escalate to anaemia, in which the bone marrow doesn’t have enough iron to produce the requisite haemoglobin for red blood cells to carry oxygen throughout the body – a serious condition that can, in extreme cases, requires blood transfusions to correct.
In low and middle-income countries, Senanayake says, where haemorrhage is a leading cause of maternal death, iron deficiency anaemia that isn’t resolved before pregnancy can undermine the body’s ability to recover from blood loss. It can also harm the brain development of the foetus.
The costs of heavy menstrual bleeding
While there’s growing scientific recognition of the medical seriousness of heavy menstrual bleeding, there’s less research on what it’s like to live with it.
Like Alston, Emily Young, a lecturer in psychology at Sheffield Hallam University in the UK, experienced heavy menstrual bleeding. She has fainted from blood loss more than once, she explains, and always carried a change of clothes as her unpredictable periods could strike at any time.
But her doctors assured her that her periods would settle down once she had a baby. Fuelled by the sting of two decades of dismissal from medical professionals, she now researches the experiences of others with heavy periods.
“It’s not just an inconvenience. It is having to structure your entire life around your menstrual cycle,” says Young.
For a study published in 2025, Young combed through online forum posts from people with heavy menstrual bleeding to bring similar experiences into focus. What she saw ranged from maddening to darkly funny, she says.
Several posts described people needing multiple blood transfusions before a doctor recognised the severity of their problem.
Others contained vivid descriptions, such as, “Yeah, if they ever luminol [a chemical used in forensics to highlight blood at crime scenes] my bathroom, I’m going to jail while they excavate my yard for the obviously dozens of murder victims”.
There were posts about dropping out of school or work, or not having a healthy sex life due to heavy menstrual bleeding. Some posts mentioned mental health issues, and others, Young says, were heartbreaking, describing suicidal thoughts because periods were so severe and life-altering.
