Pathological contributors to iron deficiency anaemia in the UK with prevalence as percentage of total4–9
| Contributor | Prevalence |
| Occult GI blood loss | |
| Common | |
| Aspirin/NSAID use | 10–15% |
| Colonic carcinoma | 5–10% |
| Gastric carcinoma | 5% |
| Benign gastric ulceration | 5% |
| Angiodysplasia | 5% |
| Uncommon | |
| Oesophagitis | 2–4% |
| Oesophageal carcinoma | 1–2% |
| Gastric antral vascular ectasia | 1–2% |
| Small bowel tumours | 1–2% |
| Cameron ulcer in large hiatus hernia | <1% |
| Ampullary carcinoma | <1% |
| Ancylomasta duodenale | <1% |
| Malabsorption | |
| Common | |
| Coeliac disease | 4–6% |
| Gastrectomy | <5% |
| Helicobacter pylori colonisation | <5% |
| Uncommon | |
| Gut resection | <1% |
| Bacterial overgrowth | <1% |
| Non-GI blood loss | |
| Common | |
| Menstruation | 20–30% |
| Blood donation | 5% |
| Uncommon | |
| Haematuria | 1% |
| Epistaxis | <1% |
GI, gastrointestinal; NSAID, non-steroidal anti-inflammatory drug.