People are mad that the first study to use blood to test how absorbent period products are was only published last month

• The first study to test the absorbency of period products using blood was published last month.
• Learning that only water or saline was used previously sparked an angry reaction online.

A study published last month that was the first to test the absorbency of menstrual products with blood instead of water or saline has sparked shock and anger online.

The study published on August 7 in the journal BMJ Sexual and Reproductive Health aimed make it easier for both consumers to make better-informed decisions about sanitary products and doctors to assess whether heavy menstrual bleeding could be a sign of underlying health problems, such as a bleeding disorder or fibroids, or could be causing anemia.

Estimates suggest that around 80 million people menstruate globally every day, and heavy bleeding affects up to a third of those who menstruate. Doctors typically measure how much blood a patient has lost during their period by assessing how many menstrual products they fill up per hour or day.

But water and saline are less viscous than menstrual blood, according to the authors of the study, and a linked editorial said that saline does not provide a clinically meaningful picture of how it feels to wear and use a tampon, for example.

The study compared 21 period products, including sanitary towels and tampons, as well as menstrual discs, cups, and period pants, which have become more widely used in recent years, and found that discs held more blood than any other product.

But the team also found that the products held less blood than stated on the label, which they suspect could be because the products weren't tested using blood.

Only the labeling of tampon absorbency levels is regulated, due to the risk of toxic shock syndrome, which means it is difficult to predict how absorbent a product will be before you buy it, the authors said.

People were angry that menstrual products were tested using saline or water, not blood

As the study was shared online, many people learned for the first time about how menstrual products are typically tested, and saw it as a symptom of wider issues around how the reproductive health of people who menstruate is under-researched and poorly understood.

According to the editorial, only one study on menstrual blood was published between 1941 and 1950, and only 400 over the past several decades. Meanwhile, around 10,000 studies on erectile dysfunction were published during the same time period.

"Um? I assumed those commercials used water because they couldn't show blood but it's really because no one…thought to test actual blood?" one person posted on X (formerly Twitter) in response to the study. The post, which amassed 9.2 million views and 120,500 likes at the time of writing, clearly resonated with many.

"Like I HAVE to be reading this wrong?? I just have to be," a second user wrote. A third called the information "SHOCKING!" while another said: "They were using water…. i am so angry rn."

The researchers used packed red blood cells to test the products instead of water or saline

The medical assessment tools doctors use to measure how much blood a patient is losing are based on tampons and pads, the study's authors noted, which means they are not a good measure for the growing number of people using alternative menstrual products, such as menstrual discs.

"I think what really motivated this study for me is the sheer number of patients in my clinic who use menstrual cups," Dr. Bethany Samuelson Bannow, study co-author and assistant professor of medicine at Oregon Health & Science University, told Stat News.

She told Insider in an email: "Period products are not created with the intent of being a standard for diagnosis, nor is assessing menstrual blood loss a standardized goal for the production.

"That's not necessarily a fault of any particular individual or company, but I do think that all the taboo and stigma around discussing menstruation has contributed to a lack of awareness and education around what is 'normal' and what is heavy."

To get a more accurate measure of absorption capacity than with saline or water, the researchers used expired packed red blood cells, which is what's left after plasma and platelets are removed from the blood. However, they noted that menstrual blood is likely more viscous than packed RBCs as it contains blood, tissue, cells, and other secretions.

Of the 21 menstrual hygiene products tested, a menstrual disc from a Chinese brand called Ziggy held the most of any product at 80 milliliters of RBCs. A menstrual disc is a disc-shaped receptacle that is folded and inserted into the vagina to sit below the cervix and catch period blood. Unlike a cup, it does not create a suction effect.

On average, menstrual discs were found to hold the most blood at 61 ml, and menstrual underwear to hold the least at 2 ml. Tampons, pads, and menstrual cups all held similar amounts, averaging between 20 and 50 ml.

The study had some limitations. Testing was conducted in a lab, which means the results may not be the same in real life. Equally, people may change their products before they are full, due to discomfort or convenience, which may overestimate heavy blood flow, the study said.

While the findings will potentially be helpful for people who menstruate, Bannow told The Guardian, "I would far rather folks with such heavy periods reach out to their physician to find out what can be done to reduce the bleeding, rather than [trying to] find a more convenient product".