‘It’s not just an inconvenience’: We’ve underestimated the health impacts of heavy periods

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.

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.

While there are treatments available for heavy menstrual bleeding, "it's totally not enough," says Erica Marsh, a professor of obstetrics and gynaecology at the University of Michigan Medical School.