Could a Menstrual Blood Test Diagnose Endometriosis Earlier?

If you’ve been told “it’s probably just bad periods,” or you’ve spent years bouncing between doctors, scans, and trial-and-error treatments, you already know the hardest part of endometriosis isn’t only the pain—it’s the delay in diagnosis. Many people wait far too long, and that delay often affects school, work, relationships, and mental health.

That’s why the idea of a non-invasive test using menstrual blood gets so much attention. Recent evidence suggests that the “chemical fingerprints” in period blood may differ in people with endometriosis—and that those differences might eventually be used as a screening test.

One early (pilot) study looked at whether fat-like molecules called lipids in a small dried spot of menstrual blood could help tell who had endometriosis and who didn’t. The results are encouraging—but it’s important to understand what this does (and doesn’t) mean for you right now.

What is a “menstrual blood lipid” test, in plain language?

Your menstrual blood contains more than blood—it also includes uterine lining tissue, fluid with inflammatory signals, and lots of molecules your body uses for structure and signaling. Lipids are one big category of these molecules. They’re not just “dietary fat”; they include compounds involved in cell membranes, inflammation, and immune signaling.

In this approach, menstrual blood is collected as a dried spot (think: a small sample blotted onto paper), then analyzed in a lab using advanced equipment to measure many lipids at once. The long-term goal is practical: if certain lipid patterns reliably match endometriosis, you could someday have a simpler test that helps clinicians decide who needs more targeted imaging, specialist referral, or surgery.

How well did it work in this early research?

In this pilot study, a model based on two specific lipids was able to separate people with endometriosis from controls with:

• Sensitivity: 81% (about 81 out of 100 people with endometriosis would test “positive”)
• Specificity: 85% (about 85 out of 100 people without endometriosis would test “negative”)

Those numbers are promising for an early-stage screen—especially because the sample collection could be relatively easy. But there’s a big catch: this accuracy was measured using internal validation (splitting the same small dataset into training/testing repeatedly). That’s useful for early development, but it often looks better than results in real-world clinics.

In other words: it’s a strong “this might be possible,” not yet “this is ready for you to order.”

What did they actually find was different in endometriosis?

This research suggests that certain lipid classes were higher in menstrual blood among people with endometriosis, including some types of:

• Ceramides and sphingomyelins (lipids often linked with inflammation and cell signaling)
• Cardiolipins (lipids associated with cellular energy structures)
• Triacylglycerols and some oxidized lipids (which can reflect inflammatory/oxidative processes)

They also reported lower levels of some phospholipid subtypes (certain phosphatidylcholines), while other related subtypes were higher. One lipid (a cardiolipin) was not only higher in endometriosis but also tended to be higher with more advanced stage in this dataset.

For you as a patient, the key point isn’t memorizing lipid names. It’s this: period blood seems to carry measurable signals that may track with endometriosis, which supports the idea that menstrual blood could become a useful diagnostic sample—more directly tied to the pelvis than a standard blood draw.

Could this replace laparoscopy, ultrasound, or MRI?

Not at this stage.

A potential menstrual blood test—if it becomes real—would most likely function as a screening or triage tool, not a full replacement for expert evaluation and treatment decisions. Here’s why:

• Endometriosis isn’t one uniform disease; lesion types, genetic and molecular signaling, as well as lesion locations vary widely.
• Imaging (especially expert ultrasound and MRI in the right hands) can identify endometriomas and deep endometriosis, and can also suggest adenomyosis or bowel/bladder involvement—information a lipid test wouldn’t provide.
• Surgery can diagnose and sometimes treat with excision at the same time, in the hands of an endometriosis excision specialist.

A realistic future pathway might look like: symptoms → non-invasive test + imaging → faster referral to a specialist → more confident decision about treatment options. But we’re not there yet.

What this means for your real life right now

If you’re hoping this could finally be “the test” that proves what you feel, it’s completely understandable. Many patients want objective validation after years of dismissal. This line of research is hopeful because it aims to reduce diagnostic delay and make evaluation more accessible.

But today, this should not change your care plan by itself. There is no clinically validated, widely available menstrual blood lipid test you can rely on for diagnosis yet. If someone is marketing a “proven” period-blood lipid test for endometriosis based on early pilot results, that’s a red flag.

Who might benefit most if this becomes a real test?

If validated in larger and more diverse groups, a dried-spot menstrual blood test could be especially helpful for people who:

• have classic symptoms but inconclusive initial evaluations
• face long waits to see an endometriosis specialist
• can’t easily access expert imaging
• want a non-invasive step to make better informed decisions before considering surgery

It could also potentially help in places where healthcare access is limited—because dried spot collection can be simpler to transport than many other biological samples.

Practical takeaways: how to use this information at your next appointment

You don’t need to bring lipid names to your doctor. You can use this to push for a more thoughtful diagnostic plan.

Here are questions worth asking (and they apply even without any new test):

• “Given my symptoms, what’s your plan to evaluate for endometriosis and adenomyosis beyond basic ultrasounds?”
• “Can you refer me for expert pelvic ultrasound or MRI with a radiologist/team experienced in endometriosis?”
• “If imaging is negative, how will we decide between medical management vs referral to an endometriosis surgeon?”
• “What’s the timeline for reassessing if treatment doesn’t work—months, not years?”

Reality check: what we still don’t know

This research is fairly early. Before any test like this can be trusted in clinics, it needs to show it works in larger independent groups and in the kinds of patients who show up in real life (different ages, weights, hormones/contraception use, bleeding patterns, comorbid adenomyosis, fibroids, PCOS, postpartum changes, etc.).

It also needs to answer practical questions patients care about:

Will results change depending on cycle day, heavy vs light bleeding, using a hormonal IUD, taking continuous birth control, or having recent surgery? What about people who don’t menstruate regularly? How often would it be wrong—and what happens to patients who get false reassurance?

For now, the most useful way to think about this is: menstrual blood is emerging as a promising place to look for diagnostic clues. It makes sense and the research is continuing. But waiting for this is not an option. You still deserve a full expert clinical evaluation based on your symptoms, exam, and appropriate imaging/referral.