Endometriosis: Symptoms, Causes, Treatment

Written by Dr. Simon Khela MBChB MRCGP, GMC Registered Doctor

Last reviewed: 03-08-2026

_________________________________________________________________________

A patient in her late twenties once told me she’d been managing "bad periods" since she was fourteen, missing school and later work for a day or two most months, and had been told by more than one clinician over the years that this was simply what her body was like. By the time she came to see me, she’d been living with debilitating pain for well over a decade. Investigations confirmed endometriosis. Her story isn’t unusual, it reflects a genuinely well-documented problem with how long this condition typically takes to diagnose in the UK.

Endometriosis affects an estimated one in ten women and people assigned female at birth of reproductive age in the UK, yet it remains widely misunderstood, both by the public and, at times, within healthcare itself. Understanding what it actually is, what causes it, and what treatment can realistically achieve is the first step toward getting the right help sooner rather than later.

This article covers:

• What endometriosis is and the current understanding of what causes it
• The symptoms to recognise, and why they're so often dismissed
• How endometriosis differs from the related but distinct condition, adenomyosis
• Diagnosis, treatment options, and what to realistically expect from each

Quick Answer: What Is Endometriosis?

Endometriosis is a condition where tissue similar to the lining of the womb (the endometrium) grows outside the uterus, most commonly on the ovaries, fallopian tubes, and the lining of the pelvis, though it can occasionally be found elsewhere in the body. This tissue responds to the menstrual cycle in the same way the womb lining does, thickening and then breaking down, but because it has no way to leave the body, it causes inflammation, pain, and, over time, scar tissue.

• Common symptoms include severe period pain, pelvic pain outside of periods, pain during sex, and heavy bleeding
• The exact cause isn't fully understood, though several biological theories and known risk factors contribute
• Diagnosis can take years, partly because symptoms overlap with other conditions and partly because period pain is often, wrongly, normalised
• There's no cure, but a range of treatments, from pain relief and hormonal therapy to surgery, can meaningfully improve symptoms and quality of life

What Causes Endometriosis?

Many patients are surprised to learn that, despite how common endometriosis is, medical science still doesn't have one definitive answer for what causes it. Several theories currently exist, and it's likely that more than one mechanism is involved.

Retrograde Menstruation

Menstrual blood flows backward through the fallopian tubes into the pelvis instead of leaving the body. This is one of the longest-standing theories, though it doesn't fully explain why some women develop endometriosis and others don't despite this being a relatively common occurrence.

Cellular Transformation

Cells outside the uterus change into endometrial-like cells under certain hormonal influences.

Immune System Factors

The body fails to clear misplaced endometrial cells effectively, allowing them to implant and grow.

Genetic Factors

Endometriosis is known to run in families, suggesting an inherited susceptibility.

Surgical Scar Implantation

A less common route where endometrial cells become implanted in a surgical scar, such as after a caesarean section.

Known Risk Factors

• A family history of endometriosis, particularly in a mother or sister
• Starting periods at a young age
• Short menstrual cycles or heavy, prolonged periods
• Never having given birth
• Certain structural abnormalities of the womb

Endometriosis Symptoms

A question I’m frequently asked is how to tell "normal" period pain apart from something that needs investigating. In practice, the pattern and severity matter more than any single symptom.

During Your Period

• Severe pain that disrupts normal daily activities, not simply mild discomfort
• Heavy bleeding, sometimes needing to change protection every one to two hours
• Pain that doesn't respond well to standard over-the-counter painkillers

At Any Time in the Cycle

• Chronic pelvic pain, in the lower abdomen or back
• Pain during or after sex
• Pain when opening your bowels or passing urine, particularly around your period
• Persistent fatigue
• Bloating, sometimes referred to informally as "endo belly"
• Difficulty conceiving

One of the most common concerns I see in practice is a patient assuming that because their pain is "just" period pain, it doesn’t warrant investigation. Severity that interferes with work, relationships, or daily life is never something to simply tolerate indefinitely.

Adenomyosis vs Endometriosis

This is a genuinely common point of confusion, partly because the two conditions share a similar underlying process and can occur in the same person at the same time.

‍

Many patients are surprised to learn that having one of these conditions doesn't rule out the other, and in some cases, overlapping symptoms make it genuinely difficult to know which is contributing more to how someone feels without proper imaging and specialist assessment.

How Is Endometriosis Diagnosed?

The average time to diagnosis in the UK has historically been reported at around eight years from the start of symptoms, a statistic that reflects real, systemic issues, including symptom overlap with other conditions and a persistent tendency to normalise severe period pain.

• Discussing your symptoms and family history with a GP is the starting point, alongside a physical and internal examination where appropriate
• Blood tests may be used to help rule out other causes of pelvic pain, rather than to diagnose endometriosis directly, since there's currently no reliable blood test for the condition itself
• Transvaginal ultrasound can identify endometriomas (cysts related to endometriosis) but often misses smaller, superficial patches of disease
• MRI scanning can help identify deeper disease, particularly affecting the bowel or bladder
• Laparoscopy, a keyhole surgical procedure allowing direct visualisation of the pelvis, remains the definitive way to confirm diagnosis, though current UK guidance doesn't require this before starting treatment based on a strong clinical suspicion

If initial assessment and treatment through primary care aren't resolving symptoms, a referral to a specialist, typically a gynaecologist, is the usual next step for further investigation.

Endometriosis and Fertility

Endometriosis is found in a significant proportion of women being investigated for infertility, though it's important to be clear that not everyone with endometriosis will have difficulty conceiving, and the relationship between disease severity and fertility impact isn't always straightforward.

• Scar tissue and adhesions can affect the fallopian tubes and ovaries, physically impacting conception
• Inflammation within the pelvis may affect egg quality or implantation
• Some women with even severe endometriosis conceive without difficulty, while others with relatively mild disease experience significant fertility challenges, which is part of why generalised reassurance in either direction isn't always helpful

For anyone trying to conceive with a known or suspected diagnosis, earlier discussion with a GP or an infertility clinic is generally more useful than waiting, since some treatment approaches for endometriosis (particularly certain hormonal therapies) are specifically not suitable while trying to conceive.

Treatment for Endometriosis

There's currently no cure for endometriosis, and treatment focuses on managing symptoms, improving quality of life, and, where relevant, supporting fertility.

Pain Relief

• Standard painkillers, including NSAIDs, are often tried first, though many patients with endometriosis find these insufficient alone
• A private prescription may be needed for stronger or more tailored pain management where standard options aren't controlling symptoms adequately

Hormonal Treatment

• The combined contraceptive pill, taken continuously or cyclically, can reduce symptoms for many women
• Progestogen-only treatments, including certain pills, injections, or a hormonal intrauterine system, work by reducing or stopping periods, limiting the hormonal stimulation that drives endometriosis activity
• GnRH analogues, used more selectively, induce a temporary menopause-like state, usually alongside "add-back" hormone therapy to manage side effects, and are typically used for shorter periods under specialist guidance

Surgical Treatment

• Laparoscopic surgery to remove or destroy visible patches of endometriosis can improve pain and, in some cases, fertility outcomes
• Removal of endometriomas (ovarian cysts related to endometriosis) may be recommended depending on size and symptoms
• Hysterectomy, with or without removal of the ovaries, is considered only in more severe, treatment-resistant cases, and even then doesn't guarantee complete symptom resolution if disease exists elsewhere in the pelvis

Supporting Approaches

• Pelvic physiotherapy for some patients with chronic pelvic pain
• Support groups and psychological support, given the genuine impact of chronic pain on mental health and daily functioning
• General health monitoring, including a general health check where heavy bleeding has raised concerns about iron levels or general wellbeing

Common Myths and Misconceptions

Myth: Painful periods are just something women have to put up with.

Severe pain that disrupts daily life is never something to simply accept without investigation, regardless of how normalised period pain has historically been.

Myth: A normal scan means you don't have endometriosis.

Ultrasound and MRI can miss smaller or superficial patches of disease. A normal scan reduces likelihood but doesn’t rule it out entirely, which is why laparoscopy remains the definitive diagnostic test where genuine doubt remains.

Myth: Getting pregnant cures endometriosis.

Pregnancy can temporarily ease symptoms for some women due to hormonal changes, but it isn’t a cure, and symptoms often return afterwards.

Myth: A hysterectomy will definitely fix it.

Removing the uterus doesn't remove endometriosis tissue located elsewhere in the pelvis, so symptoms can persist for some patients even after this surgery, particularly if the ovaries are retained.

Myth: If you're not trying to get pregnant, endometriosis doesn't need treating.

Endometriosis can cause significant chronic pain and other symptoms regardless of fertility plans, and treatment decisions should reflect the person's actual symptoms and priorities, not just reproductive plans.

Benefits and Limitations of Treatment Options

Hormonal treatments are generally effective at reducing symptoms for many women, are non-surgical, and reversible, but they don't address any existing scar tissue and aren't suitable for those actively trying to conceive. Surgical treatment can offer more definitive symptom relief and address visible disease directly, but carries the usual risks of surgery and, particularly with more extensive procedures, doesn't guarantee symptoms won't eventually return.

Being honest about this matters. No single treatment works identically for everyone, and decisions often involve balancing symptom control, fertility plans, and personal preference, ideally discussed properly with a specialist rather than assumed from general information alone.

When to See a GP

• If period pain is severe enough to affect your normal daily activities
• If you have pelvic pain outside of your period that isn't explained by another cause
• If you experience pain during or after sex that concerns you
• If you're struggling to conceive and haven't yet discussed this with a doctor
• If previous treatment for suspected endometriosis hasn't improved your symptoms

An online GP consultation or a private GP appointment is a reasonable starting point to discuss your symptoms properly and agree on next steps, whether that's initial treatment, further investigation, or a private blood test to check for related issues such as anaemia from heavy bleeding.

Frequently Asked Questions