Blood testing in menstrual research has shed new light on the significance of feminine hygiene products in women’s lives. This billion-dollar industry offers a plethora of product options, each adorned with a small absorbency label that ostensibly quantifies their blood-holding capacity. Nevertheless, recent findings suggest that this label may be less informative than consumers presume.

A team of researchers at Oregon Health & Science University made history by conducting the first study on the absorption of period products using blood. The study was posted in BMJ Sexual & Reproductive Health on August 7th and has proven to be a great advancement in menstrual science research.

Amongst the research team is co-author Bethany Samuelson Bannow, a clinician and assistant professor of hematology at Oregon Health & Science University. She began research on the absorbance of menstrual products after taking notice of female patients switching to reusable menstrual discs and cups. Bannow also took note of the little information available on menstrual science to doctors and consumers, stating in an article for Scientific American, “We realized that there wasn’t really a metric for diagnosing heavy menstrual bleeding in folks who use those products.”


For decades, scientists and advertisers have opted to use saline water instead of blood during the testing period. Saline solution is a mixture of water, salt, and bicarbonate, which is commonly employed in the product development process. The main reason why companies utilize saline solution is its cost-effectiveness compared to blood. According to the Wiley Online Library, research-quality blood costs up to $200. Meanwhile, labs can buy a full liter of saline solution for just $45.

feminine hygiene product labels

Blood is not as easily accessible as saline is. Many hospitals have frequent blood shortages owing to the high demand for patients. According to America’s Blood Center, only 3% of Americans donate blood every year. Every two seconds someone is in need of blood. Many researchers and doctors would rather utilize donated blood for sick patients rather than scientific studies. Blood is also a potential biohazard, and researchers must obtain a special license for its use in laboratories, proving to be a time-consuming cost to companies.


However, it is still essential for researchers to test menstrual products by using blood instead of saline. The different viscosities of blood and water indicate that one is much more absorbent than the other. Blood is thicker than water, containing cells, proteins, and other nutrients that make it so. Although the blood used in the study is of red blood cells rather than menstrual blood, which contains vaginal secretions and tissue that make it more viscous. However, it is a much closer approximation compared to saline.

The study conducted by the team of researchers at Oregon Health is an important step in the right direction for menstrual research. Most of our knowledge of menstrual blood metrics comes from studies conducted in the 1980s and is overdue for an update. This study provides more accurate product information displayed to consumers.

It will also aid doctors in the diagnosis of heavy menstrual bleeding. The American College of Obstetricians and Gynecologists reports that about one-third of women seek treatment for heavy menstrual bleeding. Heavy menstrual bleeding could put them at risk for anemia or be suggestive of other underlying medical problems.


The study states that the research team “found considerable variability in red blood cell volume capacity of menstrual products.” The lab results revealed that of all the twenty-one products tested, menstrual underwear had the least amount of blood (3 mL). Heavy tampons, pads, and menstrual cups hold approximately 20-50 mL, and the ultra-pads surprisingly surpass the advertised 10-20 mL range. Of all the products tested, the one that holds the greatest amount of blood is the menstrual disc. The tests resulted in a 61 mL average for menstrual discs, and one brand (Ziggy) was able to hold up to 80 mL.

Blood Testing in Menstrual Research

The results of this study further our understanding of the capacity of old and new menstrual products. This study will create an improved blood metric for clinicians, who will be better at quantifying menstrual blood loss based on product usage by patients. Women’s health will improve overall as more women get the care and products they need.


It is surreal to many women, including myself, that, in all these years, we have not tested menstrual products with blood. Dr. Paul D Blumenthal of Obstetrics and Gynecology states that approximately 800 million individuals menstruate each day globally. Menstruating is normal and healthy, however the stigma surrounding the topic has caused a major delay in research and creating a standard metric and terminology.

However, the future of menstrual science is not bleak. More studies have been conducted over the years. Dr Blumenthal describes “samples of menstrual blood being studied as a noninvasive diagnostic modality for endometriosis” among other clinical innovations. Further research and studies will support the growth, modernization and normalization of menstrual science.


DeLoughery, E., Colwill, A. C., Edelman, A., & Bannow, B. S. (2023, July 31). Red blood cell capacity of modern menstrual products: Considerations for assessing heavy menstrual bleeding. BMJ Sexual & Reproductive Health.

Heavy menstrual bleeding. ACOG. (n.d.).

Jacobs, J. W., Diaz , M., Arevalo Salazar , D. E., Tang , A., Stephens , L. D., Booth , G. S., Lehmann, C. U., & Adkins, B. D. (2023, April 25). United States blood pricing: A cross-sectional analysis of charges and reimbursement at 200 US hospitals. Wiley Online Library .

Thompson, J. (2023, August 22). No one studied menstrual product absorbency realistically until now. Scientific American.

Tyson, N., Kciuk, O., & Blumenthal , P. D. (2023, July). Going with the flow: The emergence of Menstrual Science.