Melaena (Tarry Black Stool) Is an EmergencyTarry, foul-smelling black stool (melaena) indicates significant upper GI bleeding (stomach/duodenum). Go to A&E or call 999 immediately — IV access and urgent endoscopy needed.
Colour Guide
| Blood Appearance | Likely Origin | Urgency |
|---|---|---|
| Melaena (black, tarry) | Upper GI: stomach, duodenum | Emergency — A&E |
| Dark red, mixed with stool | Lower GI: colon | Urgent — 2-week wait referral |
| Bright red, on surface/paper only | Anus/rectum: haemorrhoids, fissure | GP evaluation |
| Bright red mixed into stool | Rectal/sigmoid colon — cancer excluded first | Urgent assessment |
| Altered blood + mucus | Inflammatory bowel disease, polyp, cancer | GP → colonoscopy |
NICE 2-Week Wait CriteriaRectal bleeding + age ≥40 + change in bowel habit; or age ≥50 with rectal bleeding alone — these meet NICE FIT-testing criteria. Positive FIT test (≥10 μg/g) = colonoscopy referral. Do not ignore.
Are haemorrhoids dangerous?
Haemorrhoids are not dangerous but can cause significant discomfort and anaemia if bleeding is heavy/chronic. Treat with dietary fibre, topical creams, and sitz baths. Banding or surgery for persistent cases.
At what age should I worry about blood in stool?
Rectal bleeding in anyone over 40 with a change in bowel habit warrants urgent investigation. In people over 50, even isolated rectal bleeding requires FIT testing under NICE guidelines. Below 40 without risk factors, haemorrhoids are the most likely cause.
What is the FIT test?
Faecal immunochemical test — a home test that detects tiny amounts of human blood in stool that are invisible to the naked eye. Used in NHS bowel cancer screening. FIT ≥10 μg Hb/g triggers colonoscopy referral.
Can diet change stool colour?
Red foods (beetroot, red food colouring) can turn stool red. Iron supplements and bismuth cause black stool that can mimic melaena. Rule out dietary causes, but never assume — investigate if in doubt.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.