Urgent Referral TriggersWeight loss with: blood in stool, persistent cough/hoarse voice, difficulty swallowing, a new lump, night sweats, or age over 60 with no clear cause — requires urgent investigation.
Causes Overview
| Category | Examples |
|---|---|
| Malignancy | GI cancers, lymphoma, lung cancer |
| Endocrine | Hyperthyroidism, uncontrolled diabetes, Addison's disease |
| GI disease | Coeliac disease, Crohn's, malabsorption |
| Psychiatric | Depression, anxiety, dementia, eating disorders |
| Infection | TB, HIV, chronic infection |
| Social / functional | Food insecurity, inability to cook, dentition problems |
| Medications | Metformin, SSRIs, stimulants |
Start With BloodsInitial investigations: FBC, CRP/ESR, TFTs, fasting glucose, LFTs, U&E, calcium, LDH, PSA (men), CA-125 (women), chest X-ray, urine dip. These cover most serious causes.
The 5% Rule
A loss of 5% of body weight (e.g., 3.5 kg in a 70 kg person) in 6–12 months without dietary change is the threshold for investigation. Document the weight at each GP visit.
Is 5 kg weight loss in 3 months serious?
Potentially. 5 kg in a 70 kg person is ~7% — above the threshold for investigation. See your GP, especially if no dietary or lifestyle changes explain it.
Does cancer always cause weight loss?
Not always, and not immediately. Weight loss is more common in advanced cancers, especially GI, pancreatic, and lung cancers. However, early cancer can also cause it via metabolic effects.
Can depression cause weight loss?
Yes. Depression often reduces appetite, motivation to cook, and enjoyment of food. It's one of the most common non-malignant causes of unexplained weight loss.
What is the investigation pathway?
Initial bloods + chest X-ray. If normal: CT chest/abdomen/pelvis (staging scan). If specific symptoms: targeted endoscopy, colonoscopy, or PET scan. Findings guide next steps.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.