Does Crohn's disease cause blood in stool?

Inflammation or an ulcer in the bowel lining can cause blood to mix with stool or appear on its surface. The colour and amount can vary, and bleeding may occur with diarrhoea, urgency, cramps or mucus during active bowel inflammation. Bright red blood can also come from the lower bowel or anus, while very dark or tar-like stool may indicate bleeding higher in the digestive tract. Blood in stool is not specific to Crohn's disease, so a clinician needs the full history.

Note the colour, amount, frequency and whether the blood is mixed through the stool. Record pain, diarrhoea, fever, dizziness and changes in your usual bowel pattern. Contact your gastroenterology team or a clinician about new bleeding, especially if you have Crohn's disease or take medicines that affect bleeding. Continue prescribed treatment unless a clinician tells you otherwise, and drink fluids if diarrhoea is present.

Seek emergency help for heavy or ongoing bleeding, black tar-like stool, vomiting blood, fainting, confusion, severe weakness or shortness of breath. Prompt assessment is also needed for bleeding with severe abdominal pain, fever, a swollen abdomen or signs of dehydration. Do not wait for a routine appointment if the amount of blood is increasing or you feel unwell.

Ask whether the bleeding could reflect active Crohn's inflammation, an anal cause, infection or another bowel problem. Discuss whether you need an examination, blood tests or stool testing, and agree on the symptoms that should trigger urgent contact.