Menorrhagia Algorithm · Reasoning GP

Safety

Red Flags — Exclude Malignancy and Serious Pathology

Done

HMB can be the presenting symptom of endometrial carcinoma, cervical cancer, and serious coagulopathy. Screen before attributing to benign causes.

Intermenstrual bleeding Bleeding between periods at any age → 2WW gynaecology (endometrial/cervical malignancy until excluded)

Postcoital bleeding Bleeding after intercourse → 2WW colposcopy/gynaecology (cervical carcinoma, ectropion)

Postmenopausal bleeding ANY bleeding ≥12 months post-LMP → 2WW gynaecology. Endometrial cancer until proven otherwise.

Age >45 + new onset HMB New or worsening HMB over age 45 without clear cause → 2WW endometrial assessment (endometrial hyperplasia/carcinoma)

Failed treatment HMB persisting despite adequate medical treatment → 2WW gynaecology for endometrial biopsy

Haemodynamic instability Tachycardia, hypotension, pallor, syncope with heavy bleeding → 999 / same-day acute gynaecology (haemorrhage)

Abnormal cervical cytology history Pending smear result or recent abnormal smear + IMB/PCB → colposcopy pathway not delayed

Pelvic mass on examination Firm, irregular uterus or adnexal mass → Same-day USS + urgent gynaecology referral

Endometrial carcinoma is the commonest gynaecological malignancy in the UK (9,700 cases/year). HMB is the most common presenting symptom. The 5-year survival rate drops from 89% (stage I) to 17% (stage IV) — early detection is critical. Postmenopausal bleeding has a 10% malignancy rate, mandating urgent investigation regardless of other factors. NICE NG12 mandates 2WW referral for postmenopausal bleeding and specific patterns of abnormal uterine bleeding in older women.

Diagnose

Quantify Bleeding — NICE-Recommended Assessment

Done

NICE NG88: HMB is defined by impact on quality of life, not just volume. Formal measurement is impractical — use a structured history.

NICE definition

Excessive menstrual blood loss that interferes with physical, emotional, social, or material quality of life. Patient's perception is valid — do not dismiss.

Practical quantification

Passing clots >2.5cm (50p coin) · Flooding through clothing/bedding · Changing protection hourly for 2+ hours · Using double protection (towel + tampon simultaneously) · Restricting daily activities

Pictorial Blood Loss Assessment Chart (PBAC)

Score >100 correlates with blood loss >80mL. Useful for monitoring response to treatment. Optional — not mandatory per NICE NG88

Cycle pattern

Duration, frequency, regularity. Regular heavy periods = more likely structural (fibroids, adenomyosis) or dysfunctional. Irregular = consider ovulatory dysfunction (PCOS, thyroid), malignancy.

Associated symptoms

Dysmenorrhoea (endometriosis, fibroids, adenomyosis) · Pressure symptoms (large fibroids) · Dyspareunia (endometriosis) · Infertility concerns · Symptoms of anaemia (fatigue, dyspnoea, palpitations)

Contraception & pregnancy

Current method (IUD can cause HMB), recent cessation of hormonal contraception. Exclude pregnancy in all reproductive-age women → urine βhCG if any doubt.

NICE NG88 (2018) moved away from the 80mL/cycle criterion because it is impractical to measure and correlates poorly with patient impact. A woman passing clots the size of 50p coins has measurably different quality of life impairment — this is a legitimate clinical threshold. Ectopic pregnancy presenting as irregular heavy bleeding is missed if pregnancy is not excluded — urine βhCG takes 30 seconds and should be near-universal in reproductive-age women with abnormal bleeding.

Diagnose

Classify Underlying Cause — PALM-COEIN Framework

Done

FIGO PALM-COEIN classification guides investigations and management. Structural causes (PALM) usually need imaging or surgery; non-structural (COEIN) respond to medical treatment.

P Polyp

Endometrial or cervical polyp. HMB + IMB. Diagnosed on USS or hysteroscopy. Treat by polypectomy.

A Adenomyosis

Endometrial glands in myometrium. HMB + severe dysmenorrhoea. Bulky, tender uterus on examination. Diagnosed by USS (heterogeneous myometrium) or MRI.

L Leiomyoma (fibroids)

Most common. HMB ± pressure symptoms ± bulk symptoms. Palpable uterus. Diagnosed by USS. Treatment depends on size/location/symptoms/fertility wishes.

M Malignancy/hyperplasia

Any age but especially >45 or postmenopausal. HMB ± IMB ± risk factors (obesity, nulliparity, PCOS, tamoxifen, Lynch syndrome) → 2WW

C Coagulopathy

Von Willebrand disease (most common — 13% of HMB), platelet disorders, anticoagulant therapy. HMB from menarche, family history, easy bruising, nose bleeds. Ask about every new HMB patient

O Ovulatory dysfunction

Irregular cycles. Hypothyroidism, hyperprolactinaemia, PCOS, perimenopause. Treat underlying cause.

E Endometrial

Primary endometrial disorder (e.g., prostaglandin imbalance). Regular cycles, no structural cause, normal investigations. Commonest cause of HMB. Diagnosis of exclusion.

I Iatrogenic

Copper IUD (increases blood loss 20–50%), anticoagulants (DOAC, warfarin, heparin), SSRIs, antipsychotics, tamoxifen.

Von Willebrand disease affects 1% of the population and accounts for up to 13% of HMB referrals — it is consistently under-diagnosed because bleeding symptoms are normalised. The NICE NG88 "stop the bleeding" questionnaire (≥3 symptoms of heavy periods from menarche, bruising, nose bleeds, gum bleeds, family history) should be used to screen. Missing VWD means treating HMB medically without treating the coagulopathy — and exposing the patient to unnecessary surgical intervention.

Diagnose

Targeted Examination

Done

Abdomino-pelvic examination is essential in all new presentations of HMB to identify structural causes and exclude acute emergency.

Vital signs

HR, BP, pallor. Tachycardia + pallor → acute haemorrhage or severe anaemia → urgent action. Obesity assessment (BMI) — key endometrial cancer risk factor.

Abdominal examination

Palpate for uterine enlargement (fibroids — can reach umbilicus), adnexal mass, tenderness. Midline mass arising from pelvis → urgent USS.

Speculum examination

Cervical appearance: ectropion (bleeds on contact), polyp at os, suspicious lesion → 2WW colposcopy. Confirm IUD threads present if in situ.

Bimanual examination

Uterine size (normal = walnut, 6–8 weeks = orange, 12 weeks = grapefruit), regularity, tenderness. Bulky tender uterus → adenomyosis. Irregular hard uterus → fibroids.

Cervical smear status

Check if cervical screening is up to date. Do not defer if overdue — cytology separate from HMB assessment.

Signs of anaemia

Conjunctival pallor, tachycardia, flow murmur, koilonychia (iron deficiency). Guides urgency of anaemia treatment.

Signs of coagulopathy

Bruising, petechiae, purpura, spider naevi, hepatomegaly (liver disease → coagulopathy).

A 14-week-size fibroid uterus can be diagnosed on abdominal palpation alone — missing this finding and prescribing medical treatment without imaging delays definitive management by months. Cervical polyps at the os are visible on speculum examination and bleed easily — removing (or referring to remove) them resolves the HMB immediately. Examination findings directly determine whether USS is routine or urgent and whether referral pathways are medical or surgical.

Diagnose

Investigations

Done

NICE NG88: USS is the first-line investigation for HMB where structural cause is suspected. Bloods are mandatory.

Mandatory bloods

FBC — assess anaemia (iron deficiency anaemia in up to 30% of HMB). Ferritin even if Hb normal (iron depleted before anaemia develops). TFTs — hypothyroidism causes menorrhagia. βhCG — exclude pregnancy.

Coagulation screen

NICE NG88: Offer coagulation screen if HMB since menarche OR family/personal history of coagulopathy. Von Willebrand factor antigen + activity, Factor VIII. Refer haematology if abnormal.

Pelvic USS

First-line imaging Transvaginal preferred (better endometrial detail). Order if: structural cause suspected, uterus enlarged/irregular, failed medical treatment, age >45, IMB/PCB. Reports endometrial thickness, fibroid mapping, ovarian assessment.

Endometrial thickness

On USS: >4mm in postmenopausal → biopsy. >12mm premenopausal + risk factors → biopsy. USS cannot exclude endometrial carcinoma — biopsy required if clinical suspicion

Hysteroscopy + biopsy

Gold standard for endometrial pathology. Indicated if: USS inconclusive, endometrial abnormality on USS, failed medical treatment, IMB/PCB, age >45. Performed in secondary care.

NOT routinely needed

MRI (only if fibroid mapping required pre-surgery or adenomyosis assessment needed) · Laparoscopy (only if endometriosis strongly suspected)

NICE NG88 does not mandate USS for every HMB presentation — a woman with clearly normal examination, regular cycles, no structural symptoms, and no red flags can start medical treatment without imaging. However, if treatment fails or if there are any structural symptoms (dysmenorrhoea, pelvic pain, bulk symptoms), USS should not be delayed. Endometrial thickness >4mm on postmenopausal USS has sensitivity of 96% for endometrial carcinoma — but specificity of only 60%, so positive results require biopsy not just repeat scanning.

Refer

Referral Criteria

Done

Most HMB can be started on medical treatment in primary care while awaiting investigation results. Referral is for surgical management, malignancy exclusion, and treatment failure.

999 / Same-day

Acute haemorrhage + haemodynamic instability → A&E · Severe anaemia (Hb <70 + symptomatic) → acute gynaecology

2WW Gynaecology

Postmenopausal bleeding · IMB or PCB · Age >45 + unexplained new-onset HMB · Suspicious cervical appearance · Pelvic mass · Endometrial thickness >4mm (postmenopausal)

Urgent (2–4 weeks)

Haematology referral if coagulopathy screen abnormal · Suspected large fibroids (>3cm symptomatic) → gynaecology for surgical options discussion · HMB + infertility concerns

Routine gynaecology

HMB failing 3–6 months of adequate medical treatment · Requesting surgical intervention (endometrial ablation, myomectomy, hysterectomy) · Suspected adenomyosis wanting definitive treatment · IUD insertion for HMB treatment (if not available in primary care)

Primary care management

Regular HMB, normal examination, no red flags, ≤45 years: start medical treatment and monitor response over 3 cycles. USS can be arranged concurrently.

NICE NG88 specifically supports initiating the LNG-IUS (levonorgestrel intrauterine system) in primary care without specialist referral, as it is the single most effective medical treatment for HMB. Starting treatment without waiting for a gynaecology appointment (which may take months) significantly reduces the impact of HMB on quality of life and prevents iron deficiency anaemia from worsening. Endometrial ablation achieves patient satisfaction rates of 85–90% and avoids hysterectomy in 70% of cases — referral for this should not be delayed in women who have completed their families.

Treat

Treatment Ladder — Medical Management

Done

NICE NG88 treatment hierarchy is clear: LNG-IUS first if no contraindication. Hormonal before non-hormonal unless contraindicated. Always treat concurrent iron deficiency anaemia.

Contraception desired / no structural cause

LNG-IUS (Mirena) First-line NICE

Levonorgestrel 52mg IUS. Reduces blood loss by 71–96%. Effective for 5 years. Can insert in primary care. Most effective reversible medical treatment.

Short-term / not wanting IUS

Tranexamic acid Non-hormonal first-line

1g (2 × 500mg) TDS for up to 4 days per cycle. Reduces blood loss by 29–58%. Take only during heavy days. No effect on cycle regularity.

Dysmenorrhoea + HMB

Mefenamic acid Non-hormonal

500mg TDS during menstruation. Reduces blood loss by 25–35% AND treats dysmenorrhoea via COX inhibition. Avoid in peptic ulcer disease, asthma (NSAID-sensitive).

Full treatment ladder:

Step 1LNG-IUS (Mirena 52mg) — First choice per NICE NG88 if structural cause excluded or small fibroids (<3cm). Offer to all eligible women. Review at 3 months.

Step 2Tranexamic acid 1g TDS days 1–4 AND/OR mefenamic acid 500mg TDS during menstruation. Can combine. Use while awaiting LNG-IUS or if declined. Review after 3 cycles.

Step 3COCP (combined oral contraceptive pill) — Reduces blood loss by 40–50%. Norethisterone 5mg BD–TDS day 5–26 of cycle if COCP contraindicated. Discuss VTE risk.

Step 4GnRH analogue (e.g., leuprorelin 3.75mg IM monthly) — Pre-surgical downregulation of fibroids. Maximum 6 months. Add-back HRT to prevent hypo-oestrogenic symptoms. Secondary care initiation.

Step 5Surgical options (secondary care): Endometrial ablation (most fibroids <3cm, completed family) · Myomectomy (fibroids, fertility desired) · Hysterectomy (definitive, completed family). UAE (uterine artery embolisation) for large fibroids.

Iron deficiency anaemia treatment (treat concurrently):

Ferrous sulfate

200mg OD–BD (every other day has equivalent efficacy with fewer GI side effects). Continue 3 months after ferritin normalises (>50 µg/L). Mandatory — do not treat HMB without treating anaemia

The LNG-IUS is NICE's first-line recommendation because it outperforms all other medical treatments with 71–96% reduction in blood loss vs 29–58% for tranexamic acid, 40–50% for COCP, and only 25–35% for mefenamic acid. NNT for clinically meaningful improvement is 1.5 for LNG-IUS vs 5 for tranexamic acid. Alternate-day iron dosing exploits hepcidin regulation — once-daily dosing suppresses hepcidin for 24 hours, reducing iron absorption; alternating days allows recovery and increases total absorption by 40%. GnRH analogues without add-back HRT cause bone loss at 0.5–1% per month — add-back is not optional if treatment exceeds 3 months.

Lifestyle

Non-Pharmacological Support & Self-Management

Done

Lifestyle factors influence HMB severity, treatment response, and patient-reported outcomes. Integrate into every management plan.

Weight management BMI >30 increases oestrogen production via peripheral aromatisation → endometrial stimulation → worsens HMB. Even 5–10% weight loss reduces cycle irregularity and HMB severity. Refer to structured weight management programme.

Iron-rich diet Red meat, leafy greens, fortified cereals, legumes. Eat vitamin C alongside iron-rich foods to improve absorption. Avoid tea/coffee with meals (tannins reduce iron absorption by 62%).

Practical management planning Emergency supplies at work/in bag. Period pants as backup to towels. Dark clothing during heavy days. Discuss with employer/school if HMB affects attendance — GPs can provide supportive letters.

Exercise Regular aerobic exercise regulates prostaglandin balance and reduces dysmenorrhoea by 30–40%. Does not worsen HMB. Encourage continuation of exercise during periods.

Stress reduction Chronic stress elevates cortisol → disrupts HPO axis → worsens cycle irregularity and HMB. CBT, mindfulness, regular sleep. Refer psychological therapies if significant mood impact.

Symptom diary Cycle tracking app (Clue, Flo) or PBAC chart for 2–3 cycles. Documents severity, pattern, and treatment response. Invaluable for gynaecology referral and assessing treatment efficacy.

Avoid NSAIDs prophylactically Ibuprofen taken pre-emptively before period onset can reduce HMB by 20–25% (prostaglandin inhibition). Different from mefenamic acid strategy — practical for mild-moderate HMB.

Alcohol moderation Alcohol impairs liver metabolism of oestrogen → relative hyperoestrogenaemia. Reducing alcohol to <14 units/week may modestly improve cycle regularity.

Obesity is the strongest modifiable risk factor for HMB — adipose tissue converts adrenal androgens to oestrone, creating unopposed oestrogen stimulation of the endometrium. A systematic review showed 5–10% weight loss reduced HMB severity scores by 28% in obese women with ovulatory dysfunction. The symptom diary serves a dual purpose: it validates the patient's experience (important in a condition frequently dismissed) and provides objective data for treatment audit and referral letters. NICE NG88 specifically recommends offering women practical advice on managing HMB at work and school.

Safety

Follow-Up, Monitoring & Safety-Netting

Done

Medical treatment response should be formally assessed. Iron deficiency anaemia needs monitoring to ensure adequate repletion.

3 months

Review after 3 menstrual cycles on treatment. Assess: symptom change, PBAC score improvement, side effects (especially with LNG-IUS — spotting common in first 3–6 months). Check FBC + ferritin if anaemia was present.

6 months

If initial treatment inadequate: step up ladder (see Step 7). If on LNG-IUS with ongoing symptoms: USS to confirm correct positioning. Refer gynaecology if unresponsive to Step 3 treatment.

Ferritin monitoring

Recheck ferritin at 3 months. Target ferritin >50 µg/L (not just normal range — storage depletion persists). Continue iron supplementation until target reached.

LNG-IUS specific

Check threads at 6 weeks post-insertion (expulsion rate 5%). Annual review recommended. Replacement at 5 years (Mirena) or 3 years (Jaydess — not licensed for HMB).

Safety-net — same-day

New IMB or PCB · Pelvic pain acutely worse · Fever + discharge + HMB (endometritis) · Pregnancy symptoms (ectopic risk with IUS) · Anaemia symptoms worsening acutely

Safety-net — 999

Haemodynamic compromise: heavy bleeding + faintness + tachycardia + pallor → A&E immediately

Annual review

Reassess underlying diagnosis annually. Perimenopause changes HMB pattern — new irregularity in women >40 warrants re-investigation for endometrial pathology.

The LNG-IUS has a 5% expulsion rate in the first year, higher in women with larger uteruses. Undetected expulsion leaves the patient without contraception and without HMB treatment — the 6-week thread check is not optional. LNG-IUS irregular bleeding (spotting/breakthrough) in the first 3–6 months is expected and normal — counselling women about this prevents premature removal before the device has had time to work. After 6 months, 90% of women have significantly reduced or absent periods. Failure to counsel leads to 20% early removal rate.