Reasoning GP · Algorithm · 1-page summary
Tiredness / fatigue in adults
For: adults presenting with new tiredness or fatigue in general practice. Not for: children and young people (ME/CFS timings differ; use paediatric assessment), or a cause already found and being managed (use that condition's protocol).
Core rule: screen for red flags first, then choose tests from the history and examination. A normal screen is reassuring but does not end assessment: fatigue is often multifactorial, and ME/CFS is a positive diagnosis after exclusion, not a label of last resort.
0Stop — call 999 now — before any history
- Collapse, severe chest pain or acute breathlessness at rest → 999
- Chest pain with fatigue (ACS, post-viral myocarditis) → ECG and troponin via hospital → 999 or Same-day
- Meningism, raised intracranial pressure features or new focal neurology → 999 or Same-day
- Suicidal crisis → 999. Low mood with suicidal ideation or a passive death wish → Same-day mental health emergency assessment
1Triage — sinister features?
| Finding | Action |
|---|---|
| Red flag | Weight loss, nodes, sweats, fever, focal signs, bleeding, breathless, chest pain, severe low mood → blocks 0–2 |
| Duration | <1 month with fever → infection; gradual → systemic |
| Post-exertional | Delayed worsening → think ME/CFS; no graded exercise |
| None | Targeted bloods; sort the cause (block 4) |
2Screen — fatigue alone is not an NG12 trigger
- Persistent fatigue with pallor, fever, bruising or bleeding → consider very urgent FBC ≤48 h (leukaemia)
- Unexplained lymphadenopathy ± splenomegaly → consider cancer pathway (lymphoma); weigh B symptoms, itch
- 40+, ≥2 unexplained symptoms e.g. fatigue + weight loss (≥1 if ever smoked) → CXR ≤2 weeks. 60+, >5% weight loss in 6 months → assess, then urgent tests or cancer / non-specific symptoms pathway
- Breathless (heart failure, severe anaemia, PE), Addisonian crisis (postural drop, confusion, vomiting), sepsis/endocarditis, systemic decline → Same-day
- GCA (50+, new headache, scalp tenderness, jaw claudication, visual symptoms) → Same-day treat per local pathway, without waiting for bloods
- Jaundice 40+ → Cancer pathway; liver failure → Same-day; else Urgent hepatology. Severe anaemia or abnormal film → Urgent
3Assess — only once blocks 0–2 are answered
☐ Sleep, snoring, apnoeas ☐ PHQ-2 → PHQ-9, suicide risk ☐ Drugs (beta-blockers, sedatives, opioids, statins), alcohol, substances ☐ Heavy periods, pregnancy, postpartum, perimenopause ☐ Work, caring, domestic abuse
☐ Pallor, nodes, thyroid, liver/spleen, pulse rhythm, lying/standing BP, SpO₂, BMI ☐ Bloods: FBC, U&E, LFT, TFT, HbA1c, ferritin; CRP/ESR if plausible. B12/folate, calcium, CK, coeliac, HIV, 8–9am cortisol, ECG/BNP only if indicated. Not routinely: EBV/CMV, ANA/ANCA, MRI or CT. No blood test for OSA.
4Classify — only if the screen is negative
- Psychosocial (commonest) — stress, mood, sleep, caring, alcohol → PHQ-9/GAD-7.
- Organic — anaemia, low ferritin, thyroid, diabetes, coeliac, CKD, liver, B12/folate → treat on results.
- OSA — ≥2 of snoring, apnoeas, unrefreshing sleep, waking headache, sleepiness, nocturia, choking.
- Other — drugs, heart failure, AF, post-viral, perimenopause.
- ME/CFS — all four ≥6 weeks, activity reduced: disabling fatigue, post-exertional worsening, unrefreshing sleep, poor cognition → suspect; diagnose at 3 months if unexplained.
- Uncertain — say so (often multifactorial); book review.
5Treat today — cause-directed
- Iron deficiency: oral ferrous salt (alternate days if daily not tolerated) until ~3 months after Hb normal; find the cause. Men, postmenopausal women → FIT; ≥10 µg Hb/g → Cancer pathway
- Hypothyroidism confirmed → levothyroxine (NG145), avoid over-replacement. B12 → hydroxocobalamin 1 mg IM.
- Depression → NG222, shared decision: Talking Therapies and/or medication. ME/CFS → pacing, no graded exercise, CBT supportive only.
- All: fixed wake time, less caffeine, alcohol ≤14 units/week, activity to 150 min/week (not ME/CFS), fit note if appropriate. Doses: NICE/SPC, BNF, local formulary.
6Refer routinely
- Abnormal result → matching specialty; raised LDH or lymphocytosis → ask haematology.
- Suspected adrenal insufficiency, or hypothyroidism not responding to levothyroxine → endocrinology.
- Suspected OSA → sleep service. Untreated OSA impairs driving (DVLA).
- ME/CFS ≥3 months, alternatives considered → ME/CFS team if available. Mood predominant → mental health.
7Never reassure by
- A normal targeted blood screen — it does not end assessment.
- A normal haemoglobin — iron deficiency without anaemia is missed; ferritin rises with inflammation.
- A low Epworth score or a negative home oximetry — neither excludes OSA.
- Fatigue "explained" by thyroid disease without biochemical confirmation.
- An ME/CFS or "adrenal fatigue" label before treatable causes are considered.
- Repeat bloods instead of reassessing history, examination and differential.
8Safety-net — say it, then document it
999 “Call 999 if you collapse, get severe chest pain or sudden breathlessness at rest, or feel you might act on thoughts of ending your life.” Same day: “New weight loss, lumps, worsening breathlessness, new weakness or numbness, yellow skin, fever, night sweats or bleeding — contact us today.” Return if it worsens, limits function, sleepiness affects driving or work, or persists despite the plan.
Review: 4–6 weeks (results, response, PHQ-9). Persisting at 3 months → revisit history, examination and results; consider ME/CFS referral if criteria met. 6 months → full reassessment for malignancy, inflammatory disease or occult infection.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Mood and suicide risk, sleep, drugs, pregnancy asked
Nodes, BP, weight examined; tests chosen and actioned
Cause named or uncertainty stated; review date set
Safety-net and driving advice given
Summary of the full Reasoning GP tiredness / fatigue algorithm, which holds the detail, examination, tests and evidence. Sources: NICE NG206, NG12 (updated April 2026), HTG690, NG145, NG202, NG243, NG20, NG136, NG222, NG60; BSG iron deficiency anaemia 2021. Clinical reference — follow local policies and check doses: NICE/SPC, BNF.