When to contact a doctor
Vomiting blood or black tarry stools needs urgent medical assessment. Heavy or continuing bleeding, dizziness, faintness, severe abdominal pain, breathlessness or a racing heartbeat requires emergency care: call 108. Even small recurrent rectal bleeding should be investigated, especially with weight loss or a change in bowel habit.
What you may notice
Vomiting fresh blood or material like coffee grounds can signal upper digestive-tract bleeding. Black, sticky, tar-like stool may contain digested blood; bright red blood can come from the lower bowel or anus. Colour alone cannot reliably locate the source or show how serious the bleeding is.
Stomach and upper digestive tract
Large and small bowel
What could cause it?
Ulcers, inflammation, enlarged veins related to liver disease, diverticular disease, abnormal vessels, piles, a tear at the anus, polyps or cancer are possibilities. Iron and some medicines can darken stools, but a new concerning change should not be dismissed. Blood tests, endoscopy and sometimes CT help find the source.
How interventional radiology may help
Stabilisation and treatment through an endoscope are often the first steps. IR may embolise a bleeding artery when suitable, particularly when endoscopic control fails or the source cannot be reached. Selected bleeding from enlarged veins in liver disease needs a different venous approach. Surgery remains an option; the underlying cause still needs treatment.
Further reading: detailed assessment and treatment options
Patient information sources
References are in English.
Educational information, not a diagnosis. The causes listed are examples, not a complete list. Tests and treatment depend on your individual assessment.