Endometriosis: What It Is & Why It Takes So Long to Diagnose
Isla Oliver, DNP, CNM, ARNP
On average, it takes about 7 to 9 years from the first symptoms of endometriosis to an actual diagnosis.6 Endo a common cause pelvic pain and painful heavy periods — and has historically been one of the hardest conditions to pin down. Here’s why.
What Is Endometriosis?
Endometriosis happens when tissue similar to the lining of the uterus grows in places it shouldn't — usually on the ovaries, fallopian tubes, or the tissue around the pelvis. But it can grow anywhere, including the diaphragm, the abdominal wall, and on other organs.1
The most common symptom is pain, especially leading up to and during your period.
People with endometriosis often describe significant bloating in their premenstrual phase, often excessive menstrual bleeding, and painful, radiating cramps.2 Other signs can include pain during sex, pain with bowel movements or urinating (especially around your period), bloating, fatigue, and trouble getting pregnant.
Here's the confusing part: how bad your symptoms feel doesn't tell us how severe the spread of your endometriosis is.2 Someone with a small amount of affected tissue can be in severe pain, while someone with a lot might barely notice.
Why Blood Tests and Scans Aren't Enough
A lot of people assume a blood test or ultrasound can confirm endometriosis, and unfortunately, it’s not that simple.
There's no blood test that is actually available on the market that can diagnose it. Doctors have tried using a marker called CA-125, but CA-125 isn't specific to endometriosis and isn't sensitive enough to reliably detect it, so it isn't currently recommended as a diagnostic test.3 It can go up for lots of reasons — including just having your period. While one European company has claimed that they have created a blood test for endometriosis-specific markers, it’s not a test that can be ordered by a provider in the United States.
Imaging is very limited as well. Neither ultrasound nor MRI can reliably spot the most common type of endometriosis lesions, the small ones on the surface of pelvic tissue — and a clear scan doesn't rule the disease out.4 Scans are better at catching larger issues, like ovarian cysts caused by endometriosis, deep lesions, or severe scarring, but they can easily miss the disease entirely. This is the reason that a “normal” ultrasound doesn't mean nothing is wrong.
Why Surgery Is Currently The Only Way To Be Sure
Right now, the only way to fully confirm endometriosis is a surgery called a laparoscopy. A surgeon inserts a thin camera through a small cut in your abdomen, looks directly at the pelvic organs for any lesions, and can take a biopsy to confirm if what they see is endometriosis. Laparoscopy has historically been considered the gold standard for diagnosis, since it's the only method that lets doctors see the tissue directly.5 While this surgery gives us information, it does not cure or treat endometriosis either.
Because of this, many doctors now start treatment based on symptoms alone, without waiting for surgery, and the 2026 American College of Obstetricians & Gynecologist Recommendation states that we should be diagnosing the disorder based on symptoms, not surgery, to expedite treatment.12
This combination of unreliable tests and an invasive gold-standard test is a major reason diagnosis has historically taken so long.
Conditions That Look a Lot Like Endometriosis
Part of the delay comes from the fact that endometriosis symptoms overlap with several other conditions, so doctors often have to rule those out first — or risk treating the wrong one first.
• Adenomyosis. Sometimes called endometriosis's “cousin,” this is when similar tissue grows into the muscle wall of the uterus itself instead of outside it.7 It also causes heavy, painful periods. Adenomyosis can be seen on ultrasound imaging.
• Irritable bowel syndrome (IBS). Endometriosis and IBS are two common conditions with symptoms that overlap a lot, which causes confusion and delays diagnosis.8 Both can cause bloating, cramping, and changes in bowel habits. Symptoms of IBS can also worsen around your period.
• Interstitial cystitis (painful bladder syndrome). This condition and endometriosis share so many symptoms — pelvic pain, pain during sex, urinary urgency — that doctors sometimes call them the “evil twins” of pelvic pain.9 Some people end up with both.
• Pelvic inflammatory disease and ovarian cysts can also cause similar pain and get confused with endometriosis early on.
Most of these conditions also don’t have one simple test, so sorting out which one (or ones) you are dealing with often takes real time and a doctor willing to dig.
Treatment Options — and Why They Overlap
Treatment usually focuses on managing pain and, for some people, fertility. There are a few approaches you can choose to take.
First is pain management – we don’t have many medications on the market that work particularly well for uterine pain, but NSAIDs, like ibuprofen or other prescription strength options help to reduce pain and reduce the inflammation caused by tissue growing where it isn't supposed to.
Preventing ovulation – this can be done in many ways, the most reliable being birth control pills, but it's not the only option. If we prevent ovulation, we prevent the signal your body gives to grow uterine lining anywhere it might be growing.
Thinning the uterine lining – This can be done without reliable ovulation suppression, but everyone’s body is different, so sometimes the hormonal signal that thins your endometrium and endometriosis can also prevent ovulation. It also depends on which specific medication you select.
Surgery to remove endometriosis tissue can also relieve pain, and some people are able to get pregnant afterward if fertility was the issue. Without a hormonal treatment after surgery, the endomtriosis will grow back over time.
In general, difficulty conceiving is typically caused by a physical blockage related to endometriosis. Either in the form of endometriosis cells or scar tissue blocking the fallopian tubes or some part of the ovary. Most people with endometriosis still ovulate regularly, so clearing any blockage can help with conception. Preventing scar tissue by using things like birth control can also help conserve your fertility for the future.
There is some overlap worth knowing: many of these same treatments — birth control, hormonal therapy, pain relievers — are also first-line treatments for adenomyosis, general menstrual pain, and painful bladder syndrome.11 That means starting treatment doesn't always confirm which condition you actually have. Some people improve on hormonal treatment and never get a clear diagnosis; others try several treatments before finding what works.
One important consideration with endometriosis is that we don't know how to prevent the spread or progression of the condition without a hormonal medication. You have many options to choose from, but the source of the condition isn't somethine we have figured out how to suppress through lifestyle changes or non-hormonal medications.
The Bottom Line
Given our current limitations, endometriosis is genuinely hard to definitively diagnose — not because doctors aren't paying attention, but because the tools available (blood tests, imaging) fall short, and the most reliable option (surgery) is invasive. If your pain is dismissed as “just bad periods,” it's worth pushing for more answers. You know your body better than anyone!
References
1. Mayo Clinic. Endometriosis — Symptoms and Causes. mayoclinic.org
2. Mayo Clinic News Network. Women's Wellness: Learn About Endometriosis. newsnetwork.mayoclinic.org
3. National Center for Biotechnology Information (NIH). Biomarkers of Pelvic Endometriosis. pmc.ncbi.nlm.nih.gov
4. Endocrinology Advisor. ACOG Issues New Guidance on Endometriosis Evaluation and Diagnosis. endocrinologyadvisor.com
5. Medscape (eMedicine). Endometriosis Workup. emedicine.medscape.com
6. National Center for Biotechnology Information (NIH). Endometriosis: New Insights and Opportunities for Relief of Symptoms. ncbi.nlm.nih.gov
7. Liv Hospital. Endometriosis Symptoms and Conditions. int.livhospital.com
8. National Center for Biotechnology Information (NIH). Comparison of Sociodemographic Factors, Lifestyle, and Gastrointestinal Symptoms Between Patients With Endometriosis and IBS. ncbi.nlm.nih.gov
9. Healthline. Interstitial Cystitis and Endometriosis: Symptoms, Treatments. healthline.com
10. Cleveland Clinic. Endometriosis: Causes, Symptoms, Diagnosis & Treatment. my.clevelandclinic.org
11. National Center for Biotechnology Information (NIH). Hormonal Treatment of Endometriosis: A Narrative Review. ncbi.nlm.nih.gov
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