Heavy Menstrual Bleeding Is 'Decades of Overdue Research on Women'! Severe Anemia and Brain Fog Risks — Don’t Ignore These Signs

From ages 12 to 13, Michelle Alston spent the worst days of her period in the school nurse’s office. She endured severe pain while dealing with blood leakage. “I was taught from a young age that this was normal—that this was just something you had to learn to cope with,” she said. She felt weak and unlike her peers in managing menstruation. It wasn’t until her early 40s that she realized her weakness wasn’t a matter of willpower—her menstrual flow was abnormally heavy.

When menstrual bleeding is so heavy it impairs quality of life, doctors call it “heavy menstrual bleeding,” a serious medical condition. Population studies worldwide estimate that 10% to 30% of reproductive-age women experience heavy bleeding like Alston’s. Due to underreporting and widespread misunderstanding of what constitutes excessive bleeding, some studies suggest the actual proportion could reach half of all reproductive-age women.

Heavy menstrual bleeding may also signal other health issues; if untreated, it can lead to serious consequences like anemia. Yet only recently have researchers begun to deeply investigate the harms of heavy bleeding and seek better diagnostic methods and treatments.

In the biomedical research database PubMed, searching “menstrual blood” yields only about 400 studies over the past decade. In contrast, searching “semen” returns over 15,000 studies.

“Women have probably had decades—perhaps even centuries—of research underinvestment,” said Dr. Jackie Maybin, a gynecologist at the University of Edinburgh and lead researcher of the “The Missed Vital Sign” study. “And I think now is the time.”

How Much Blood Is Too Much?

For researchers, heavy menstrual bleeding is defined as losing more than 80 milliliters of blood per cycle, passing clots larger than a quarter (24.26 mm in diameter), or periods lasting longer than seven days.

But for people experiencing menstruation, there is no standardized or quantifiable way to measure blood loss. How many bathroom trips per day? How many pads or tampons changed? How many underwear stained? These everyday experiences lack uniform standards.

Some clinicians try to help patients assess their flow by showing them a series of images depicting pads and tampons progressively soaked with menstrual blood. But this method is also imprecise, as not all period products absorb equally, and differences between products can be vast.

Thus, determining what constitutes “too much” bleeding isn’t simple. Often, doctors rely on one key criterion: whether the bleeding is affecting the patient’s quality of life.

“Sometimes patients don’t realize their bleeding isn’t normal—and that there are ways to manage it,” said Dr. Adwoa Christy, clinical professor of obstetrics, gynecology, and reproductive sciences at UC San Francisco.

Alston frequently stained her sheets and clothes with menstrual blood. Once, she left a bloodstain on a pristine white chair in a mobile phone store. She assumed she had done something wrong—perhaps she just needed different period products to control the flow.

She was told to accept severe cramps and embarrassing leaks as normal. In other parts of the world, menstrual taboos and stigma are even more severe.

“I think in my region, many people may not complain about this; they might not even see a doctor due to normalization of pain and social stigma,” said Professor Hemantha Senanayake, emeritus professor of obstetrics and gynecology at the University of Colombo and president of the Asian Society of Endometriosis and Adenomyosis.

Endometriosis and adenomyosis are conditions that can cause heavy menstrual bleeding.

While gynecologists may know to ask detailed questions to identify heavy bleeding, clinicians outside gynecology may overlook these signs.

Alston waited nearly 30 years before anyone diagnosed her with heavy menstrual bleeding. And she is far from alone.

Heavy Bleeding Is More Than a Symptom

While heavy menstrual bleeding is a problem in itself, it’s often a symptom of a larger issue.

It can be caused by various conditions, including polyps, fibroids, cancer, blood disorders, ovulation problems, and endometrial diseases like endometriosis.

When women first start menstruating or enter the menopausal transition, hormonal fluctuations often cause heavier periods—though this still requires medical attention.

Treating these symptoms can reduce bleeding, but scientists still don’t fully understand how these conditions affect blood loss.

“There’s been a lot of research focused on fibroids themselves, but much less on why they cause heavy bleeding,” said Maybin. She notes fibroids are non-cancerous growths in the uterine muscle.

On the other hand, untreated heavy bleeding can trigger new problems, such as iron deficiency. Iron is a vital mineral essential for healthy cells, immune function, muscles, skin, hair, and nails.

When iron levels drop, symptoms like brain fog, dizziness, shortness of breath, easy bruising, and hair loss may occur.

In other words, the damage from heavy bleeding persists even on non-menstrual days. Studies estimate over 40% of women with heavy periods also suffer from iron deficiency. Alston is part of this statistic.

She often felt cold and had intense cravings for ice—a strange but telling sign of iron deficiency, which researchers still don’t fully understand.

If untreated, iron deficiency can progress to anemia. Anemia occurs when bone marrow lacks sufficient iron to produce hemoglobin, the protein in red blood cells that carries oxygen. It’s a serious condition that, in extreme cases, may require blood transfusions.

Senanayake notes that in low- and middle-income countries, postpartum hemorrhage is a leading cause of maternal death. If women enter pregnancy with untreated iron-deficiency anemia, their ability to recover from blood loss is weakened, potentially harming fetal brain development.

An Unprecedented Number of Periods

Among placental mammals, fewer than 2% have menstrual cycles: elephant shrews, certain bats, spiny rats, and primates.

Research suggests that for most of human history, women had more children, limiting their lifetime menstrual cycles to about 40. But human life patterns are changing. In high-income countries especially, women have fewer children and may experience up to 400 periods in their lifetime.

This makes menstruation—and heavy menstrual bleeding—more medically and socially relevant than ever before.

The Cost of Heavy Bleeding

While the scientific community is increasingly recognizing heavy menstrual bleeding as a serious medical issue, research on how patients actually live with it remains limited.

Like Alston, Emily Young, a psychology lecturer at Sheffield Hallam University in the UK, also experienced heavy menstrual bleeding. She said she fainted multiple times due to blood loss.

Because her cycle was unpredictable, she always carried spare clothes. Yet doctors assured her her periods would improve after childbirth.

After enduring two decades of dismissal and denial from healthcare professionals, she is now researching the experiences of other women with heavy bleeding.

“This isn’t just inconvenient. It means you have to structure your entire life around your menstrual cycle,” she said.

In a 2025 study, Emily Young analyzed online forum posts by women with heavy bleeding to make these shared experiences more visible.

She found content ranging from infuriating to darkly humorous. Some posts described needing multiple blood transfusions before doctors recognized the severity. Others included vivid descriptions: “If someone ever used luminol (a forensic chemical to detect blood at crime scenes) to check my bathroom, I’d definitely be arrested—because they’d dig up my backyard, convinced there are dozens of murder victims buried there.”