Adenomyosis and endometriosis are cousins, not twins. In adenomyosis, tissue similar to the womb lining grows into the muscle wall of the womb itself. In endometriosis, similar tissue grows outside the womb, in places like the ovaries, bowel and pelvic lining. Adenomyosis is more often diagnosed after 30 and tends to show up as heavy, painful periods and a bulky, tender womb. Endometriosis can start from your first period and often brings pain that spreads well beyond your womb. And here is the part almost nobody tells you: you can have both at the same time.^1,2

You're not imagining it. If you've been told your periods are "just bad", that you need to "push through", or that it's "probably your age", you are in large company. Endometriosis UK found that the average wait for an endometriosis diagnosis in the UK is now 8 years and 10 months.³ Adenomyosis gets even less airtime. If you're still working out where adenomyosis fits next to other hormonal conditions, our guide to PCOS vs endometriosis is a good companion read, and so is endometriosis and inflammation: what the research actually shows.

This guide breaks down the 7 key differences between adenomyosis and endometriosis, how each one is diagnosed in the UK, what to ask your GP, and how to support yourself day to day while you get answers. If your cycle has been running your life for a while, we'll also show you where our plant-based Endoplus fits into a daily routine (alongside medical care, never instead of it).

In this article

• What is the difference between adenomyosis and endometriosis?
• What are the 7 key differences?
• Can you have adenomyosis and endometriosis at the same time?
• What does adenomyosis feel like?
• Why does adenomyosis get missed?
• How do you get an adenomyosis diagnosis in the UK?
• What helps day to day?
• FAQ

What is the difference between adenomyosis and endometriosis?

Adenomyosis grows inside the womb's muscle wall. Endometriosis grows outside the womb. Both involve tissue similar to the womb lining.

Both conditions involve tissue that behaves a lot like the lining of your womb (the endometrium). The difference is where it ends up.

• Adenomyosis: the NHS describes it as the lining of the womb starting to grow into the muscle in the wall of the womb.¹ It stays inside the uterus.
• Endometriosis: cells similar to the womb lining grow in other parts of the body, most often around the pelvis: the ovaries, fallopian tubes, bladder and bowel.²

That one difference in location shapes almost everything else: the symptoms you notice, the scan you need, and the treatment options on the table. Here is the quick version.

	Adenomyosis	Endometriosis
Where the tissue grows	Into the muscle wall of the womb	Outside the womb (ovaries, tubes, bowel, bladder, pelvic lining)
Who it's usually diagnosed in	More common after 30, often after having children	Anyone from their first period to menopause
Signature symptom	Heavy, painful periods	Pelvic pain, often beyond your period
Womb size	Often enlarged and tender	Usually normal size
Usual route to diagnosis	Transvaginal ultrasound or MRI	Scans can help; laparoscopy confirms
Can affect other organs?	No, it stays within the womb	Yes
Does a hysterectomy remove it?	Yes, it is the only definitive treatment	Not on its own, because the tissue sits outside the womb

Sources: NHS, Schrager et al. (2022), NICE NG73. See references below.

What are the 7 key differences between adenomyosis and endometriosis?

Location, typical age, main symptom, womb size, how they're diagnosed, how they affect fertility, and which treatments can remove them.

1. Where the tissue grows

This is the big one. Adenomyosis is an inside job: the tissue burrows into the myometrium, the thick muscle layer of the womb.⁴ Endometriosis is an outside job: the tissue sets up camp around the pelvis and, less commonly, further afield.² Think of adenomyosis as a problem with the walls of the house, and endometriosis as a problem in the garden.

2. Who it tends to affect

The NHS says adenomyosis is more commonly diagnosed in women over 30, and that being over 30 and having given birth are risk factors.¹ A 2022 clinical review in American Family Physician notes most people are diagnosed between 40 and 50, with risk rising with age, number of pregnancies and previous procedures on the womb.⁴ Endometriosis is diagnosed in women and girls from puberty through to menopause.²

That age difference matters. If you're in your late 30s or 40s and your periods have got steadily heavier and more painful, adenomyosis deserves a place on the list, not just "perimenopause".

3. The signature symptom

Heavy bleeding is the headline symptom of adenomyosis. The 2022 review puts heavy menstrual bleeding at 40 to 60% of people with adenomyosis, and notes around a third have no symptoms at all.⁴ Endometriosis is more often defined by pain: severe period pain, pelvic and lower back pain, and pain with sex, going to the toilet or peeing.²

There is plenty of overlap. Both can cause painful periods, heavy periods, pelvic pain and painful sex. That overlap is exactly why the two get confused (or why one gets found and the other gets missed).

4. The "adenomyosis belly"

Because adenomyosis lives in the muscle of the womb, it can make the womb bigger, softer and tender. Doctors describe it as "boggy".⁴ The NHS lists bloating and a feeling of heaviness in the tummy among adenomyosis symptoms.¹ That is the "adenomyosis belly" so many women search for: a lower tummy that looks and feels swollen, sometimes all month. Endometriosis is also well known for bloating (often nicknamed "endo belly"), but it doesn't usually enlarge the womb itself.

5. How each one is diagnosed

Adenomyosis is usually diagnosed with imaging. A transvaginal ultrasound picks up around 84% of cases, and MRI is better at confirming it.⁴ Endometriosis can sometimes be seen on ultrasound or MRI, but the NHS notes the only way to confirm it is a laparoscopy, a keyhole procedure where a camera looks inside your tummy.^2,5

Translation: a "normal" scan doesn't rule out endometriosis, and a scan not done by someone looking for adenomyosis can miss it.

6. How they relate to fertility

Both conditions are linked with fertility challenges, for different reasons. With adenomyosis, researchers think changes in the inner muscle zone of the womb affect how the womb contracts and how sperm travels. One meta-analysis found people with adenomyosis had a 28% lower chance of clinical pregnancy with IVF.⁴ With endometriosis, the NHS notes it can make it harder to get pregnant.²

Your diagnosis is a starting point, not a verdict. Plenty of people with either condition do conceive. If you're trying, ask for a referral to a fertility specialist who knows both conditions.

7. What removes them

Both conditions are managed with options like pain relief, hormonal contraception, the hormonal coil and surgery.^1,2 The difference shows up at the surgical end. A hysterectomy is the only definitive treatment for adenomyosis, because the condition lives inside the womb.⁴ For endometriosis, removing the womb doesn't remove tissue growing elsewhere in the pelvis, which is why specialist excision surgery exists. Either way, that is a big decision to make with a specialist, not a blog post.

Can you have adenomyosis and endometriosis at the same time?

Yes. They often occur together, and in some studies most people with endometriosis also showed signs of adenomyosis on MRI.

This is the part that changes everything for a lot of women. A German study in Human Reproduction used MRI to look at 160 women with endometriosis and found signs of adenomyosis in 79% of them, rising to 90% in women under 36.⁶ Other estimates are lower: the 2022 review puts overlap at around 11% overall but 49 to 66% in deep endometriosis.⁴ The numbers vary because studies use different scans and different groups of patients, but the message is consistent. If you have one, it's worth asking about the other.

Why does this matter? Because if you've had endometriosis surgery and your heavy, painful periods haven't budged, adenomyosis could be part of the picture. For more on the myths that keep women going in circles, read 9 endometriosis myths still believed in 2026.

What does adenomyosis feel like?

Heavy, painful periods, pelvic pain, bloating or heaviness in the tummy, and pain during sex. Some people have no symptoms at all.

The NHS lists these adenomyosis symptoms:¹

• During your period: painful periods and heavy bleeding
• At other times: pelvic pain, bloating or a heavy feeling in your tummy, and pain during sex

And here's how to tell if "heavy" means heavy. The NHS describes heavy periods as needing to change your pad or tampon every 1 to 2 hours, or passing clots larger than about 2.5cm (the size of a 10p coin).⁷ If that sounds like your normal, it isn't one you have to accept.

Your body is trying to tell you something. Heavy bleeding month after month can also leave you running on empty, so ask your GP whether a blood test to check for iron deficiency anaemia makes sense for you.⁷ If pain is the bigger issue for you, our guide to period pain relief covers what the evidence supports.

Why does adenomyosis get missed?

Its symptoms overlap with endometriosis, fibroids and "normal bad periods", and standard scans don't always look for it.

I built MyOva for women who feel unheard by the system, and adenomyosis is one of the clearest examples I know of a condition hiding in plain sight.

Hormonal literacy isn't complicated. It's just rarely taught. Here's why adenomyosis slips through the net:

• The symptoms look familiar. Heavy, painful periods get filed under "some women just have bad periods".
• It hides behind other conditions. Fibroids are present in around half of people with adenomyosis, and endometriosis often overlaps too.⁴ Once one condition is found, the search often stops.
• The scan matters. Ultrasound works well when the person scanning is looking for adenomyosis. A quick scan for something else can miss it.⁴
• Age gets blamed. In your 40s, heavier periods are easy to wave away as perimenopause.
• Women's pain gets minimised. In Endometriosis UK's 2024 research, 47% of people saw their GP 10 or more times before being diagnosed with endometriosis.³

So how common is adenomyosis? A UK study at a London gynaecology clinic found adenomyosis on transvaginal ultrasound in 20.9% of women attending.⁸ That's roughly 1 in 5 women in that clinic. Hardly rare.

How do you get an adenomyosis diagnosis in the UK?

See your GP with a symptom diary, ask about a pelvic exam and transvaginal ultrasound, and request gynaecology referral or MRI if needed.

This is what I wish someone had told me: walk into that appointment with evidence, not just a feeling. Here's a simple plan.

1. Track 2 to 3 cycles. Note how often you change pads or tampons, the size of any clots, your pain score (0 to 10), when pain happens, bloating, and days you missed work or plans.
2. Book a GP appointment about your periods only. Not "and while I'm here". Give it the full slot.
3. Use the word. Say: "I'd like to rule out adenomyosis and endometriosis." Naming both helps.
4. Ask about a pelvic examination and a transvaginal ultrasound. The NHS says your GP may examine you and arrange an ultrasound or MRI.¹ Ask whether the scan can specifically look for adenomyosis.
5. Ask about blood tests. With heavy periods, check for iron deficiency anaemia.⁷
6. Ask for a gynaecology referral if your symptoms continue, if treatment isn't working, or if your scan is "normal" but you're not.

Not being heard? You are allowed to ask for a second opinion. Our article on what the Women's Health Strategy means for PCOS and endometriosis explains what you can expect from the NHS.

What helps day to day while you get answers?

Medical care comes first. Alongside it, heat, gentle movement, iron checks, steady meals, good sleep and a consistent daily routine help.

Start with medical options

The NHS lists treatments for adenomyosis including the hormonal coil (IUS), other hormonal contraception, tranexamic acid, anti-inflammatory painkillers, and, if other treatments haven't worked, surgery.¹ These are conversations to have with your GP or gynaecologist, and you're entitled to understand the pros and cons of each.

Then build your everyday toolkit

• Heat: heat pads and hot water bottles are on the NHS's own list of ways to manage symptoms.¹
• TENS machines: also listed by the NHS for pain.¹
• Steady, colourful meals: plenty of vegetables, oily fish, beans, wholegrains and iron-rich foods. Our guide to anti-inflammatory eating for hormonal health walks through it.
• Movement you can tolerate: walking, stretching or yoga on harder days.
• Sleep: protect it fiercely in the days before and during your period.
• Consistency: small daily habits beat dramatic one-off fixes.

Where MyOva fits

Let's be clear. No supplement treats adenomyosis or endometriosis, and anyone who says theirs does is selling you a story. Food supplements are not medicines, and they are not a substitute for diagnosis or medical treatment.

What a well-designed supplement can do is add consistency to your daily routine. It's not a magic fix. But it gives your body what it's often missing. That's the thinking behind Endoplus and the rest of our range.

If your cycle hits your mood and energy as hard as it hits your body, Cycle Support is built around how you feel through the month.

And for the hot-water-bottle evenings, a warm ritual counts for a lot.

Frequently asked questions

Is adenomyosis worse than endometriosis?

Neither is "worse" across the board. Both can range from no symptoms to pain and bleeding that take over your life. Adenomyosis is more often linked with heavy bleeding and an enlarged womb, while endometriosis can affect organs outside the womb. How it affects you is what counts.^1,2,4

Can adenomyosis be seen on an ultrasound?

Often, yes. Transvaginal ultrasound detects around 84% of adenomyosis, and MRI is more specific at confirming it.⁴ It helps when the person scanning is specifically looking for it, so it's worth asking.

Is adenomyosis cancer?

No. Adenomyosis is a benign (non-cancerous) condition of the womb.⁴ That said, any new or unusual bleeding, such as bleeding between periods, after sex or after menopause, should always be checked by your GP.

What is an adenomyosis belly?

It's the swollen, heavy or bloated lower tummy some people with adenomyosis notice. It happens because adenomyosis can enlarge the womb, and the NHS lists bloating and tummy heaviness as symptoms.^1,4

Can adenomyosis affect fertility?

It can. Adenomyosis is associated with lower pregnancy rates in IVF, likely because of changes in the womb's inner muscle layer.⁴ Many people still conceive, so speak to a fertility specialist about your options.

Does the pill help adenomyosis?

Hormonal contraception, including the combined pill, progestogen-only pill, patch and hormonal coil, is listed by the NHS as a treatment option for adenomyosis symptoms.¹ Your GP can talk you through which may suit you.

Conclusion

Adenomyosis grows into the muscle of the womb. Endometriosis grows outside it. They share symptoms, they often turn up together, and both are too often waved away as "just bad periods". If your periods are heavy, painful or getting worse, track your symptoms, name both conditions to your GP, and ask for the right scan.

You're not imagining it, and you don't have to wait nearly nine years to be taken seriously. Get the medical answers first, then build a daily routine that has your back.

Further reading

• Endometriosis and Inflammation: What the Research Actually Shows
• 9 Endometriosis Myths Still Believed in 2026 (And What's True)
• PCOS vs Endometriosis: What's the Difference?
• Period Pain Relief: What Actually Works
• Anti-Inflammatory Eating for Hormonal Health

References

1. NHS. Adenomyosis.
2. NHS. Endometriosis.
3. Endometriosis UK. Years of being "dismissed, ignored and belittled": Endometriosis UK urges improvement to deteriorating diagnosis times. 1 March 2024.
4. Schrager S, Yogendran L, Marquez CM, Sadowski EA. Adenomyosis: Diagnosis and Management. American Family Physician. 2022;105(1):33-38.
5. NICE. Endometriosis: diagnosis and management (NG73).
6. Kunz G, Beil D, Huppert P, Noe M, Kissler S, Leyendecker G. Adenomyosis in endometriosis: prevalence and impact on fertility. Evidence from magnetic resonance imaging. Human Reproduction. 2005;20(8):2309-2316. doi:10.1093/humrep/dei021
7. NHS. Heavy periods.
8. Naftalin J, Hoo W, Pateman K, Mavrelos D, Holland T, Jurkovic D. How common is adenomyosis? A prospective study of prevalence using transvaginal ultrasound in a gynaecology clinic. Human Reproduction. 2012;27(12):3432-3439.

References