If you’ve ever felt confused, dismissed, or overwhelmed trying to understand endometriosis, you’re not alone. This condition affects around 1 in 10 women and people assigned female at birth, that’s roughly 190 million people worldwide. Despite being so common, it’s still poorly understood, hard to diagnose, and often not taken seriously.
This post breaks down what endometriosis actually is, why it’s so hard to diagnose, and how looking at the whole body (not just “the pelvis”) can help you understand and manage it better.
What is endometriosis, in plain terms?
Think of the lining inside your uterus (your womb), the tissue that builds up each month and then sheds as your period. Endometriosis is when tissue similar to that lining ends up growing in places it shouldn’t: on the ovaries, on the outside of the uterus, on the bowel, the bladder, and sometimes even further away, like the lungs.
This misplaced tissue behaves a bit like the tissue inside the womb, it responds to your hormones and can bleed a little. But because it’s in the wrong place, that blood has nowhere to go. This is part of what causes the inflammation, pain, and scarring associated with the condition.
It’s important to know: nobody fully knows why endometriosis happens. For years, doctors thought it was simply caused by period blood flowing backwards into the pelvis instead of out of the body (called “retrograde menstruation”). But most people have some backward flow during their period, and only some develop endometriosis, so it’s not the whole story. Today, it’s understood as a condition involving several body systems: your hormones, your immune system, your genes, and even things in your environment.
The four stages – and why they don’t tell you much about your pain
Doctors stage endometriosis from 1 to 4, based on how much tissue is found and where, usually seen during a surgery called a laparoscopy (a small camera inserted through the belly button). Stage 4 is the most extensive.
Here’s the part that surprises a lot of people: the stage doesn’t predict how much pain you’re in. Someone with “just a little” endometriosis (stage 1) can be in severe, debilitating pain. Someone with widespread disease (stage 4) can have minimal symptoms at all.
Why does it take so long to get diagnosed?
This is one of the most frustrating parts of endometriosis. In the UK, it currently takes an average of over 9 years from when symptoms start to when someone is actually diagnosed. Nearly half of people see their GP 10 or more times before anyone even suspects endometriosis.
Why does it take so long?
- Standard scans often miss it. Regular ultrasounds and MRIs frequently can’t see the small patches of tissue that cause endometriosis. Spotting them takes a specially trained ultrasound expert and not every clinic has one.
- The only sure way to diagnose it is surgery. A laparoscopy, where a surgeon looks inside your pelvis with a camera, is still considered the most reliable way to confirm endometriosis. That’s a big, invasive step to ask someone to take just to get answers.
- Symptoms are often written off as “normal period pain.” This is one of the biggest reasons for delay, and can be one of the biggest sources of frustration for people living with the condition.
Good news: guidelines have changed (2024)
In November 2024, the UK’s official medical guidelines (called NICE guidelines) were updated in an important way. The update said two big things:
- Skilled ultrasound scans should now be used as a first option, alongside or instead of MRI, to look for signs of endometriosis, as long as the person doing the scan has the right training.
- Doctors are now encouraged to start treatment based on your symptoms and history, even if a scan comes back “normal.” In other words, a clear scan should no longer be used as proof that nothing is wrong.
This is a genuinely meaningful shift, because for years many people were told “your scan is clear, so it can’t be endometriosis”, which we now know isn’t reliable.
A new blood test
One of the most exciting recent developments is a blood test for endometriosis. In 2025, a lab called Kephera Diagnostics launched the first commercially available blood test in the US, called EndomTest™. Instead of requiring surgery, it looks for specific markers in your blood, combined with information like your age and weight, to help identify a likely diagnosis.
Other similar blood tests are also being developed by researchers, some looking at tiny molecules in the blood called microRNAs. These tests aren’t yet a full replacement for surgery, and they’re not widely available everywhere yet, but they represent real hope for a faster, less invasive way to get answers in the future.
What does it actually feel like to live with?
Symptoms vary a lot from person to person, but commonly include:
- Pelvic pain, often worse around your period
- Pain that spreads beyond the pelvis, sometimes down the legs or into the lower back
- Bloating (sometimes called “endo belly”), nausea, or feeling sick
- Changes in your bowels; constipation, diarrhoea, or pain when going to the toilet
- Pain when passing urine
- Feeling exhausted, even after rest
- Pain during or after sex
Fertility
Endometriosis is closely linked with difficulty getting pregnant. Estimates vary, but roughly 1 in 3 to 1 in 2 people with endometriosis experience some kind of fertility challenge. This can happen for a few reasons, scar tissue changing the shape of the pelvis, inflammation affecting egg quality, or the fertilised egg having a harder time implanting. It doesn’t mean pregnancy isn’t possible; it just means it can be more complicated for some people.
Mental health
This is a part of the picture that doesn’t get talked about enough. Research shows that living with endometriosis is strongly linked to depression and anxiety — and when you look across the best studies available, at least 1 in 3 people with endometriosis are dealing with a diagnosable mental health condition.
This may not be just about living with the pain either (although that’s part of it). Scientists think there’s also a biological link: the same inflammation happening in your body because of endometriosis may also be affecting your brain chemistry and mood directly. So if you’ve struggled with your mental health alongside endometriosis, this may not be a coincidence.
Why functional medicine looks at the whole body
Endometriosis isn’t just a “pelvic” problem. It affects hormones, the immune system, the gut, and even how your body handles iron. Functional medicine looks at all of these connected pieces, rather than treating endometriosis as one isolated issue. Here’s what that looks like in plain terms.
Your hormones and inflammation feed each other
Oestrogen (a hormone) fuels endometriosis, that part is well known. What’s less well known is that the misplaced tissue doesn’t just respond to oestrogen from your ovaries. It can actually make its own oestrogen.
This locally-made oestrogen then triggers inflammation. And that inflammation, in turn, causes the tissue to make even more oestrogen. The cycle helps explain why endometriosis can be so persistent and why it causes both hormonal symptoms and inflammation-based symptoms (like pain and fatigue) at the same time.
This is also part of why the tissue doesn’t respond as well as it should to progesterone (another hormone that would normally help calm things down). This is called “progesterone resistance.”
Your gut plays a bigger role than you’d think
Your gut is home to trillions of bacteria, and some of them are directly involved in how your body handles oestrogen. Certain gut bacteria produce a substance that can “reactivate” oestrogen your body was trying to get rid of, sending it back into circulation instead of letting it leave the body. If your gut bacteria are out of balance (something called “dysbiosis”), this could potentially add to your overall oestrogen load.
There may also be a connection between endometriosis and a condition called SIBO (small intestinal bacterial overgrowth) – basically, bacteria growing in a part of the gut where there shouldn’t be so much of it. A 2025 study found that 91.9% of women with endometriosis tested positive for SIBO or a related overgrowth, compared to 83.1% of women without the condition. That’s part of why looking after gut health is such a common focus in functional approaches to endometriosis.
The “high ferritin, but still exhausted” puzzle
This one confuses a lot of people, including some doctors. Ferritin is a marker on your blood test that’s supposed to show how much iron you have stored. Normally, low ferritin means low iron, and that’s treated with iron supplements.
But in endometriosis, chronic inflammation can trick this system. Inflammation causes your liver to release more of a hormone called hepcidin, which essentially “locks” iron inside your cells instead of letting it circulate where your body needs it. The result? Your ferritin can look completely normal, or even high, on a blood test, while you’re still genuinely running low on usable iron and feeling exhausted because of it.
This matters practically, because it explains why standard iron tablets sometimes don’t help much (and can occasionally make heavy bleeding worse) if the real problem is inflammation trapping the iron you already have, rather than a simple lack of iron.
Immune system and environment
Your immune system’s job is to spot cells that don’t belong and clear them away. In endometriosis, this process may not work as well as it should, which may be part of why misplaced tissue is able to survive and grow in the first place.
There’s also growing research interest in everyday chemicals, things like BPA (found in some plastics) and phthalates (found in some cosmetics and packaging), and their possible link to endometriosis. The evidence isn’t conclusive, but it’s consistent enough that it may be beneficial to reduce exposure where it’s easy to do, for example, storing food in glass rather than plastic, or choosing simpler personal care products.
Menopause: it doesn’t always just go away
A lot of people are told, “don’t worry, it’ll get better after menopause.” For many, this may be true, since endometriosis needs oestrogen to grow, and oestrogen drops sharply at menopause, symptoms often do ease off or disappear.
But this isn’t guaranteed. Somewhere between 2 and 4% of people past menopause still live with endometriosis. Some had it before and it never fully went away; a smaller number are, confusingly, diagnosed with it for the very first time after menopause. People who had more severe symptoms before menopause seem more likely to have ongoing issues afterward.
What about HRT (hormone replacement therapy)?
If you’ve had endometriosis and you’re going through menopause, hormone replacement therapy (HRT) isn’t off the table, but it does need a bit more thought than it might for someone without that history. Here’s why: since endometriosis feeds on oestrogen, taking oestrogen on its own (without anything to balance it) can sometimes wake the condition back up.
The type of hormone used and how it’s delivered (patches and gels versus tablets, for example) can also make a difference to your overall risk profile.
None of this means that you can’t use HRT or it is unsafe for you, it just means the conversation is a bit more personal, and it’s worth having with a doctor or menopause specialist who understands endometriosis specifically, rather than getting generic menopause advice.
What can actually help – a functional medicine starting point
None of the below replaces medical care or a proper diagnosis, but alongside your treatment, here’s where a functional, whole-body approach tends to focus:
Calm the inflammation. Since inflammation is so central to how endometriosis behaves, reducing it, through gut health, diet, and identifying your personal triggers, could address part of the actual mechanism.
Support your body’s ability to clear used oestrogen. A few things that may help:
- Foods that may gently support healthy oestrogen balance, based on early research: white button mushrooms, green tea, pomegranate, nettle tea, and milk thistle. Alcohol seems to work in the opposite direction.
- Foods rich in an amino acid called methionine, found in eggs, fish, meat, seeds (like sesame and pumpkin), and soy – Your body uses methionine in a process called methylation to help clear out used hormones.
- Zinc, turmeric, and resveratrol, which are commonly used for their general anti-inflammatory support.
- A high-fibre, plant-diverse diet can support your gut and could help to properly clear oestrogen rather than reabsorbing it.
Look after your gut. Given how strong the SIBO and dysbiosis connections are, this is often one of the most useful places to start, sometimes with proper testing rather than guesswork.
Get your iron checked properly. Rather than just looking at ferritin on its own, ask whether inflammation might be part of the picture, this can completely change what kind of support you actually need.
Don’t skip the mental health piece. Given how strongly endometriosis is linked with anxiety and depression, and the likely biological (not just emotional) connection, supporting your nervous system and mental wellbeing is a genuine, evidence-based part of managing this condition.
Think about your environment where it’s easy to. Reducing exposure to certain plastics and simplifying personal care products is a small, low-effort step some people choose to take, given the ongoing research in this area.
The bottom line
Endometriosis is common, complicated, and still not fully understood by science, but our understanding is improving quickly. We now know much more about why it causes the symptoms it does… The medical guidelines have been updated and now take your symptoms more seriously (even without a “clear” scan), and we’re on the edge of having real, non-invasive tests that could change diagnosis for good.
If you think you might have endometriosis, or you’ve already been diagnosed and want extra support alongside your medical care, looking at the whole picture, hormones, gut, immune system, iron, and mental health. This could make a real difference, alongside (never instead of) working with your doctor or gynaecologist.
If you have symptoms of endometriosis, please talk to your GP or a gynaecologist.
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