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Period Pain (Dysmenorrhoea): Causes, Types & Symptoms UK
A clinically reviewed conditions guide to dysmenorrhoea — primary vs secondary period pain, why prostaglandins cause cramping, causes of secondary pain including endometriosis, and treatment options.
Period pain (dysmenorrhoea) is one of the most common gynaecological complaints in the UK. It affects the majority of women who menstruate at some point in their lives, and is severe enough to disrupt daily activities in around 20%. It is not something that should simply be endured — effective treatments exist, and severe or worsening period pain always warrants investigation for an underlying cause.
What Is Period Pain?
Dysmenorrhoea — the medical term for painful periods — describes cramping pain in the lower abdomen and pelvis that occurs around the time of menstruation. It is classified into two distinct types with different causes, different clinical courses, and different management approaches.
Period pain is not a single condition. Primary dysmenorrhoea is a normal (if uncomfortable) physiological response to menstruation — driven by prostaglandins produced in the uterine lining. Secondary dysmenorrhoea has an underlying pathological cause — most commonly endometriosis — and requires investigation and targeted treatment.
Primary vs Secondary Dysmenorrhoea
| Primary dysmenorrhoea | Secondary dysmenorrhoea | |
|---|---|---|
| Definition | Painful periods without identifiable pelvic pathology | Painful periods caused by an identifiable pelvic condition |
| Age of onset | Usually within the first few years of menstruation starting; teens and young adults | Can begin at any age; often develops in women who previously had manageable periods |
| Pain timing | Begins a few hours before or just as bleeding starts; peaks within 24–48 hours; resolves as flow diminishes | Often starts earlier (days before), lasts longer, may be present throughout the cycle in some conditions |
| Associated symptoms | Nausea, headache, fatigue, loose bowel motions (prostaglandin effects) | Heavy periods, pain with sex (dyspareunia), bladder/bowel symptoms — depend on the underlying cause |
| Cause | Excess prostaglandin production in the endometrium | Endometriosis, adenomyosis, fibroids, ovarian cysts, pelvic inflammatory disease |
| Treatment | NSAIDs, hormonal contraception, heat | Treat the underlying condition; hormonal and surgical options depend on the cause |
Why Period Pain Happens: The Prostaglandin Mechanism
Primary dysmenorrhoea is directly driven by prostaglandins — particularly PGF2α and PGE2 — produced in the endometrium (uterine lining) in the days leading up to and during menstruation.
When progesterone levels fall at the end of the luteal phase, endometrial cells release arachidonic acid, which is converted by COX enzymes into prostaglandins. These prostaglandins act on the myometrium (uterine muscle), causing:
- Myometrial contractions — the uterus contracts to shed the endometrial lining; in dysmenorrhoea, these contractions are abnormally intense and frequent
- Uterine ischaemia — intense contractions reduce blood flow to the uterine muscle, producing ischaemic pain similar to that of a muscle cramp
- Sensitisation of pain receptors — prostaglandins sensitise peripheral pain receptors in the pelvis, amplifying pain signals
- Systemic effects — prostaglandins entering the circulation cause nausea, vomiting, diarrhoea, headache, and flushing
This prostaglandin mechanism is the reason NSAIDs are so effective for primary dysmenorrhoea. NSAIDs inhibit COX enzymes, directly reducing prostaglandin production — they target the cause of the pain, not just the symptom. They are most effective when taken at the first sign of pain or even before it starts.
Symptoms
- Cramping lower abdominal pain — the core symptom; can range from dull aching to severe spasms; often radiates to the lower back and inner thighs
- Nausea and vomiting — caused by systemic prostaglandin effects
- Diarrhoea or loose stools — prostaglandins increase gut motility
- Headache — common, also prostaglandin-mediated
- Fatigue — pain itself is exhausting; sleep disruption compounds this
- Bloating — fluid retention in the days before menstruation
How Severe Can Period Pain Be?
Primary dysmenorrhoea is often dismissed as a minor inconvenience, but for many women it is genuinely debilitating. Around 20% of women with dysmenorrhoea report pain severe enough to prevent normal daily activities. It is a leading cause of school and work absence in young women in the UK.
Severity tends to improve with age and after pregnancy. Hormonal contraception typically reduces symptoms significantly. However, worsening pain that was previously manageable, pain outside the menstrual period, or pain accompanied by heavy bleeding should always be investigated for secondary causes.
Causes of Secondary Dysmenorrhoea
| Condition | Key features |
|---|---|
| Endometriosis | Most common cause of secondary dysmenorrhoea. Endometrial tissue grows outside the uterus; pain is often cyclical and progressive, worsens over time, and is associated with deep dyspareunia and subfertility. Affects around 10% of women of reproductive age. |
| Adenomyosis | Endometrial tissue within the myometrium; causes heavy, painful periods; more common in women over 30; often associated with an enlarged uterus. |
| Uterine fibroids | Benign smooth muscle tumours of the uterus; can cause heavy and painful periods; rarely malignant. |
| Ovarian cysts | Functional or pathological; pain is often unilateral; investigation with pelvic ultrasound. |
| Pelvic inflammatory disease (PID) | Ascending genital tract infection, often STI-related; causes chronic pelvic pain and dyspareunia; may be subtle or asymptomatic. |
| Intrauterine device (IUD) | Copper IUD in particular can worsen dysmenorrhoea in some women; progestogen-releasing IUS (Mirena) typically reduces it. |
Diagnosis
Primary dysmenorrhoea is diagnosed clinically — based on the characteristic pattern of pain, timing, age of onset, and absence of features suggesting secondary disease. No specific investigation is needed if the history and examination are consistent with primary dysmenorrhoea.
Investigation is indicated if: pain is severe or worsening; there are features of secondary dysmenorrhoea (deep dyspareunia, heavy bleeding, intermenstrual pain); pain is not responding to NSAIDs and hormonal contraception; or subfertility is a concern. Pelvic ultrasound is the first-line investigation for suspected structural pathology. Laparoscopy remains the definitive investigation for endometriosis.
Treatment Overview
| Approach | Detail |
|---|---|
| NSAIDs (first-line for primary) | Ibuprofen and naproxen both effective — start at the onset of pain or when bleeding begins; naproxen’s longer half-life means fewer doses needed; take with food |
| Combined oral contraceptive pill | Reduces endometrial prostaglandin production; very effective for primary dysmenorrhoea; also used in endometriosis management |
| Progestogen-only methods | Hormonal IUS (Mirena) significantly reduces dysmenorrhoea; useful if contraception also needed |
| Heat | Local heat (heat pad, hot water bottle) has moderate evidence for efficacy; comparable to low-dose ibuprofen in some studies; safe and easy to use alongside NSAIDs |
| Secondary dysmenorrhoea | Treatment targets the underlying condition (e.g. hormonal suppression for endometriosis, surgical options for fibroids) |
Prescription NSAIDs for period pain at Access Doctor — naproxen and ibuprofen 600mg: Prescription pain relief →
When to Seek Help
- Period pain that is getting progressively worse over successive cycles
- Pain that begins earlier in the cycle or does not resolve when bleeding ends
- Pain during sex (deep dyspareunia) — this suggests secondary pathology
- Very heavy periods alongside pain
- Pain not responding to NSAIDs and hormonal contraception
- If you are concerned about your fertility
Seek urgent care if you develop sudden severe pelvic pain — this may indicate a ruptured ovarian cyst, ectopic pregnancy, or pelvic inflammatory disease, all of which require prompt assessment.
Frequently Asked Questions
What causes period pain?
Primary period pain is caused by prostaglandins produced in the uterine lining at the time of menstruation. Prostaglandins trigger intense uterine contractions, reduce blood flow to the uterine muscle, and sensitise pain receptors. Secondary period pain has an underlying cause — most commonly endometriosis, but also adenomyosis, fibroids, or ovarian cysts.
Why are NSAIDs so effective for period pain?
NSAIDs inhibit COX enzymes, directly reducing prostaglandin production. Because primary dysmenorrhoea is caused by excess prostaglandins, NSAIDs target the mechanism of pain rather than just masking it. They are most effective when taken at the first sign of pain or before it starts — not waiting until pain is severe.
What is the difference between primary and secondary dysmenorrhoea?
Primary dysmenorrhoea is painful periods without any underlying pelvic pathology — the most common type. Secondary dysmenorrhoea is caused by an identifiable condition such as endometriosis, adenomyosis, fibroids, or pelvic inflammatory disease. Secondary dysmenorrhoea often causes worsening pain over time and symptoms outside the menstrual period.
When should I see a doctor about period pain?
See a doctor if your pain is getting progressively worse, begins before your period or continues after it ends, is accompanied by pain during sex or very heavy bleeding, or is not adequately controlled by NSAIDs and hormonal contraception. These features suggest secondary dysmenorrhoea that requires investigation.
Can I get prescription pain relief for period pain online?
Yes. Prescription NSAIDs including naproxen and ibuprofen 600mg are available at Access Doctor following a short online consultation reviewed by GPhC-registered pharmacist independent prescribers. GPhC pharmacy #9011198.
References
- NICE CKS. Dysmenorrhoea. Updated 2023. cks.nice.org.uk/topics/dysmenorrhoea
- Marjoribanks J et al. Nonsteroidal anti-inflammatory drugs for dysmenorrhoea. Cochrane Database. 2015.
- NHS. Period pain. nhs.uk/conditions/period-pain
- RCOG. Endometriosis: diagnosis and management. NG73. 2017.
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional. In a medical emergency, call 999.
