Fuente de la imagen, Serenity Strull/ BBC
For years, Emma Backlund, like many women, didn’t give much thought to her menstrual cycle. But in 2023, when the biotechnology startup NextGen Jane requested a sample of her menstrual blood, Backlund readily collected eight tampons from one cycle and mailed them to the company’s laboratory in Oakland, California.
The request was unusual, but straightforward and Backlund was happy to contribute, especially if it could assist future generations avoid the painful experiences she faced growing up. Understanding menstrual health is increasingly recognized as vital for overall wellness.
“When I started my period at 11, I thought I was dying,” Backlund, a 27-year-ancient graduate student from Minnesota, recalled. “I told my mom I needed to go to the hospital. And pretty much every period I’ve had since then has been like that. I would vomit every month. I missed social activities and school. It was a constant, searing, stabbing, tearing pain.”
It took 13 years for Backlund to be diagnosed with endometriosis, a chronic and debilitating condition where tissue similar to the lining of the uterus grows outside of it.
Endometriosis affects an estimated 190 million people worldwide – roughly one in ten women of reproductive age – causing heavy periods, debilitating pelvic pain, bladder or bowel problems, and even infertility.
Obtaining a diagnosis often takes between five and twelve years, as it did for Backlund. Diagnosis typically requires a laparoscopy, a surgical procedure involving a small camera inserted into the pelvic cavity, explained Ridhi Tariyal, co-founder and CEO of NextGen Jane.
That’s why Tariyal and other leaders in innovative startups are working to develop a better diagnostic test – one that is faster, cheaper, less invasive than surgery, and capable of revealing more than just an endometriosis diagnosis.
They believe the key lies in menstrual blood.
A Wealth of Medical Information
Medical professionals have examined urine samples for millennia, dating back to ancient Babylonian and Sumerian times, around 6,000 years ago. Stool and venous blood have also been studied for a century or two. However, menstrual blood has historically received little clinical attention.
It’s a complex fluid: half is normal blood, while the rest consists of proteins, hormones, bacteria, endometrial tissue, and cells shed from the vaginal canal, cervix, fallopian tubes, and ovaries.
“You get access to cell types and other molecular characteristics that aren’t possible with whole blood, saliva, or other sample types,” Tariyal said. “It’s basically a natural biopsy providing insights into the reproductive organs.”
NextGen Jane sends specially designed cotton tampons to volunteers like Backlund and has analyzed over 2,000 menstrual samples from more than 330 women since its founding in 2014.
Fuente de la imagen, Serenity Strull/ BBC
“It can be used [menstrual blood] to look for any condition affecting the uterus, and there are many,” noted Christine Metz, a reproductive biologist at Northwell Health’s Feinstein Institutes for Medical Research.
Metz began studying menstrual blood to identify biomarkers for endometriosis over a decade ago, but is now interested in exploring whether this bodily fluid could provide clues about other conditions, such as endometrial cancer, adenomyosis – where the uterine lining grows into the muscular wall of the uterus – and endometritis, an inflammation of the uterine lining.
“Menstrual effluent is very valuable for understanding uterine health, which we don’t have access to otherwise,” Metz emphasized. “It’s a very unique biological specimen.”
One study identified 385 proteins present exclusively in menstrual blood.
Beyond its monthly availability, menstrual blood offers a more holistic view of uterine health compared to the small tissue sample obtained during an endometrial biopsy.
“The uterus is roughly the size of a grapefruit, so you don’t get a global assessment [with an endometrial biopsy],” explained Metz, who asks study volunteers to collect samples using a menstrual cup.
“But menstrual effluent is the entire endometrium shed.”
Searching for Distinct Biomarkers
Because scientific research has long overlooked menstrual blood, it’s still unclear whether endometriosis possesses unique biomarkers reliable enough for a diagnostic test.
However, Metz and her research partner, geneticist Peter Gregersen, have studied over 3,700 women, with encouraging results to date.
“There are many differences,” Metz said.
For starters, women diagnosed with endometriosis have significantly fewer uterine natural killer (NK) cells, which play a role in early pregnancy by facilitating embryo implantation, placental development, and protection against infection.
“They are involved in fertility, so having very few is not good,” Metz said.
Her team also observed a key difference in stromal fibroblasts, which help repair and regenerate the uterine lining after each period. In the presence of endometriosis, the cells showed more inflammatory markers and were less able to induce changes that help prepare the uterus for pregnancy. This has also been linked to other conditions, such as polycystic ovary syndrome (PCOS) and recurrent miscarriages.
Metz’s lab also found that the expression of certain genes was altered in patients with endometriosis. Collectively, these differences are what doctors could potentially look for with a non-invasive diagnostic test for endometriosis based on menstrual blood analysis.
Metz hopes to apply for FDA approval for a home diagnostic kit in 2027.
Meanwhile, NextGen Jane researchers are extracting and sequencing messenger RNA (mRNA) from menstrual blood to search for endometriosis-specific biomarkers. To date, they’ve identified several markers they believe can reliably distinguish endometriosis from healthy cases in infertile women.
A U.S. Study involving hundreds of women with endometriosis is underway to confirm these findings, Tariyal said. In May 2025, NextGen Jane received a $2.2 million grant to fund clinical validation of a menstrual test for endometriosis in infertile patients.
Beyond Reproductive Health
But menstrual blood’s utility extends beyond endometriosis. NextGen Jane’s function has revealed links between uterine health and aging. “These are preliminary data,” Tariyal cautioned, “but there’s a clear trend between declining estrogen levels in the body – which is the definition of aging – and menstruation.”
Their observations also suggest menstrual blood could one day help identify autoimmune diseases like hypothyroidism or hyperthyroidism, where the thyroid gland releases insufficient or excessive amounts of thyroxine and triiodothyronine, hormones that control metabolism.
“People with endometriosis often have some sort of autoimmune disease,” Tariyal noted.
Given the body’s shift from inflammation to scar-free healing throughout the menstrual cycle, studying menstrual blood could offer a novel model system for inflammatory and immune-mediated diseases like rheumatoid arthritis, lupus, and multiple sclerosis, Tariyal said.
Fuente de la imagen, Serenity Strull/ BBC
Menstrual blood has also shown promise in detecting diabetes. In studies conducted between 2021 and 2024, researchers at California-based startup Qvin found that average blood sugar levels measured in menstrual blood reliably reflected blood sugar levels throughout the body.
These findings paved the way for the first and only FDA-approved menstrual health test to measure blood glucose in 2024: a sanitary pad called Q-Pad, which features a removable strip to collect blood that users mail to Qvin’s labs for analysis.
Qvin also demonstrated, in a 2022 study conducted in Thailand, that samples collected with its patented pad detected high-risk strains of the human papillomavirus (HPV), which can increase the risk of cervical cancer, better than traditional vaginal cytology.
A larger clinical trial is currently underway in the U.S. To validate these findings.
Starting this year, the trial will also examine whether Q-Pad can be used to detect sexually transmitted infections like chlamydia and gonorrhea, said Mads Lillelund, Qvin’s co-CEO.
Lillelund hopes to subsequently analyze markers of health such as thyroid and reproductive hormones, inflammatory markers, and even antibodies indicating an immune response to SARS-CoV-2.
Similarly, Berlin-based startup theblood is validating a test kit to help predict endometriosis, early menopause, polycystic ovary syndrome (PCOS), and fertility problems. They previously demonstrated in a small study that levels of vitamin A and D in menstrual blood corresponded to levels measured in whole-body blood, though at consistently lower levels.
“Our goal is for women to have faster access to diagnosis, better treatment, and better prevention,” said Isabelle Guenou, co-founder of theblood in 2022. Guenou suffered severely from endometriosis as a child, with a diagnosis taking eight years and requiring multiple surgeries.
Menstrual blood may even indicate the type of toxins one is exposed to, according to a small 2022 study by Metz that detected phenols, parabens, phthalates, and other environmental contaminants in the menstrual blood of four volunteers.
The Menstrual Revolution
Despite these advances, much of menstrual blood remains a mystery. The biggest challenge, many researchers agree, is that we haven’t yet identified all the components present and how these may change rapidly during menstruation.
Research is still in its early stages, largely due to cultural stigmas surrounding the topic, even today, with numerous unflattering euphemisms used to refer to menstruation.
Fuente de la imagen, NextGen Jane
“We’ve all been indoctrinated that it’s a taboo topic that shouldn’t even be talked about,” Metz lamented.
Adding to the challenge is the historical bias toward male subjects in medical research and the relative lack of funding for studies on women’s health. Globally, research on women’s health accounted for only 5% of global research and development funding in 2020.
“Most drug discovery has been focused primarily on men, possibly white men, with little ethnic or gender diversity,” Lillelund said. “More money is invested in male pattern baldness than in endometriosis.”
researchers of menstrual blood have had to invent, refine, and standardize protocols for sample collection, preservation, and processing. Menstrual effluent can vary drastically from woman to woman in terms of flow, viscosity, and other factors. “In this field, we’re all a bit flying blind,” Tariyal said. “There’s a lot of novel research and development that needs to be investigated.”
But a menstrual revolution is on the horizon. “The effort is getting stronger,” Tariyal said, referring to the renewed interest from patients, researchers, and investors. The Massachusetts Institute of Technology (MIT), for example, launched a $10 million initiative in July 2025 to deepen our understanding of the impact of menstrual cycles on immunology.
Menstrual blood banks are also emerging worldwide. The goal is to create “an ecosystem for researchers where they can access samples quickly, efficiently, and responsibly,” explained British entrepreneur Karli Büchling, who is helping to create Europe’s first menstrual biobank. Her team will soon begin collecting samples from women in the UK using patented home kits, and hopes the biobank will be open to researchers for a small fee by the end of 2026.
Many women, including Backlund, who live with the painful daily reality of endometriosis and other uterine conditions, say this type of research is long overdue. Growing up with painful periods and wondering what was wrong with her “was really lonely and isolating,” Backlund said. But if menstrual blood researchers achieve their mission of creating a non-invasive diagnostic tool, she added, the next generation of girls will receive faster treatment and avoid the physical and emotional suffering she endured as a child.
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