Reasoning GP · Algorithm · 1-page summary
Loss of appetite and weight loss in adults
For: adults with loss of appetite (anorexia) or unintentional weight loss. Not for: under-18s (paediatric and CAMHS pathways). Anorexia nervosa is a separate condition: see its rows.
Core rule: unexplained weight or appetite loss needs a documented plan — weigh, examine, test, check NG12, safety-net. In an eating disorder no single BMI decides risk; normal bloods exclude nothing.
0Stop — 999 or same-day admission — do not wait for tests
- Suspected adrenal crisis (vomiting, collapse or hypotension) → 999 + hydrocortisone 100 mg IM/IV now.
- Hypercalcaemia: corrected Ca >3.5 mmol/L, or any level with confusion, vomiting, severe dehydration or AKI → 999. 3.0–3.5 mmol/L → Same-day assessment; admit if symptomatic.
- Unstable: collapse, syncope, haemodynamic instability, severe dehydration, hypoglycaemia, severe electrolyte disturbance, bradycardia, long QTc, organ failure, severe malnutrition, refeeding syndrome → 999 / Same-day admission
- Eating disorder with high MEED risk on the whole picture (not BMI alone), or significant suicide/self-harm risk → Same-day, with eating-disorder and acute teams.
1Triage — what kind of problem is it?
| Finding | Action |
|---|---|
| NG12 criterion | Block 2 route → Urgent |
| Suspected eating disorder | MEED physical risk check + immediate community eating-disorder referral → Urgent |
| High refeeding risk (block 5) | No unsupervised feeding or ONS; call the dietetic, eating-disorder or acute team → Urgent |
| None | First-line tests; results reviewed within 2 weeks |
2Screen — NG12 (updated April 2026)
- Dysphagia, or ≥55, weight loss plus upper abdominal pain, reflux or dyspepsia → Suspected cancer pathway; gastric mass → consider it.
- Jaundice ≥40 → Suspected cancer pathway. ≥60, weight loss + diarrhoea, back/abdominal pain, nausea, vomiting, constipation or new diabetes → consider urgent CT.
- Unexplained haemoptysis ≥40 → Suspected cancer pathway. ≥40, ≥2 unexplained symptoms incl. weight/appetite loss (1 if ever smoked) → CXR ≤2 weeks
- Lower GI symptoms → FIT; ≥10 µg Hb/g or strong concern → refer.
- ≥60, unexplained weight loss, no site criterion → consider urgent tests or non-specific symptoms pathway. Nodes + night sweats → consider lymphoma referral.
3Assess
☐ Weigh vs previous weights; BMI, MUST ☐ Lying/standing BP, pulse, temperature, hydration ☐ Wasting, jaundice, pigmentation, nodes, abdomen, mood ☐ FBC, ESR/CRP, U&E, LFT, adjusted Ca, HbA1c, TSH, albumin, urinalysis; ferritin, coeliac serology, pregnancy test where relevant ☐ ECG if compromised, purging, abnormal electrolytes, bradycardia, QT-risk drug or suspected eating disorder. Not CA19-9, CEA or CA125 for isolated anorexia.
4Classify — only if blocks 0–2 are negative
- Medicines (commonest reversible) — GLP-1 agonists, SSRIs, metformin, opioids, digoxin (check level) → change after weighing indication and withdrawal risk.
- Depression → PHQ-9. Eating disorder — restriction, fear of weight gain, purging; SCOFF ≥2 supports assessment.
- Endocrine / GI — Addison's (pigmentation, postural drop → 9 am cortisol, endocrine advice), thyroid, uraemia, coeliac, IBD.
- Social — isolation, food insecurity, dental pain, alcohol (AUDIT-C ≥5 → brief intervention).
- Uncertain — normal first-line tests but weight still falling → NG12 or non-specific symptoms pathway, not tumour markers.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Food first: fortify, small frequent meals. Consider ONS if intake stays poor, swallow safe and malnourished or at risk — after refeeding risk check.
- High refeeding risk (CG32: BMI <16, loss >15% in 3–6 months, no intake >10 days or low K/PO₄/Mg; or two of BMI <18.5, loss >10%, no intake >5 days, alcohol/drugs) → team agrees feeding; oral thiamine 200–300 mg daily before and for 10 days.
- Nausea: antiemetic by cause; metoclopramide ≤5 days; domperidone ≤30 mg/day, ≤1 week, not with cardiac or QT risk.
- No GP appetite stimulants: megestrol, dexamethasone, olanzapine are specialist only; mirtazapine only for clear depression.
6Refer routinely
- MUST ≥2, frailty, cachexia → dietitian (urgent if rapid decline, dysphagia or refeeding risk).
- Positive coeliac serology, suspected IBD, gastroparesis → gastroenterology.
- Depression → NHS Talking Therapies (psychiatry if severe); isolation → meals services, lunch clubs.
- Cancer cachexia → palliative care; aim for comfort, not weight.
7Never reassure by
- Normal first-line bloods while weight still falls.
- A normal BMI or weight in a suspected eating disorder.
- A negative SCOFF, or normal bloods in an eating disorder.
- The patient's estimate of weight lost — weigh and compare.
- A low MUST score (misses refeeding risk).
- Tumour markers, or open-ended "watch and wait" with no review date.
8Safety-net — say it, then document it
999 “Call 999 if you collapse, become confused, or keep vomiting and feel faint, or if you have thoughts of harming yourself and cannot stay safe.” Same day “If you cannot keep fluids down, feel very weak, get palpitations or breathlessness, or notice trouble swallowing, coughing blood, yellow skin, vomiting blood or blood from the back passage — contact us today.”
Review: results within 2 weeks, then in 1–4 weeks by weight trend and risk. Remote/OOH: weigh face to face; suspected eating disorder → in-person observations, bloods, ECG.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Weighed and compared; MUST and refeeding risk recorded
First-line tests sent; results owner and date set
Medicines, mood, eating disorder and alcohol screened
Safety-net given; review in 1–4 weeks booked
Summary of the full Reasoning GP loss of appetite and weight loss algorithm, which holds the detail, examination, investigations and evidence. Sources: NICE NG12 (updated April 2026), HTG690, NG69, CG32, NG31; RCPsych MEED CR233; BAPEN MUST; MHRA Drug Safety Updates. Clinical reference — follow local cancer, eating-disorder and dietetic pathways and check doses: NICE/SPC, BNF.