Does ulcerative colitis cause blood in stool?

Inflammation and small ulcers in the bowel lining can cause blood to mix with stool or appear on toilet paper. It may occur with diarrhoea, urgency, mucus, cramps, or frequent small bowel movements. Bright red blood often comes from the lower bowel, but colour alone cannot identify the cause. Haemorrhoids, anal fissures, infections, medicines, and other bowel conditions can also cause bleeding, so new or unexplained blood should not be self-diagnosed.

Arrange a medical appointment and describe the colour, amount, frequency, and whether it is mixed with stool. Mention pain, diarrhoea, fever, weight change, medicines, and any known bowel disease. Keep drinking fluids, especially if stools are loose. Do not stop prescribed ulcerative colitis treatment or start a new medicine without advice; your clinician may need to check for active inflammation, infection, or anaemia.

Seek urgent help for heavy or continuous bleeding, black tar-like stool, dizziness, fainting, severe abdominal pain, a swollen abdomen, repeated vomiting, or profound weakness. Bleeding with fever or rapid worsening also needs prompt assessment. If you feel unwell or cannot keep fluids down, do not wait for a routine appointment.

Ask what may be causing the bleeding, whether tests are needed, how to monitor for anaemia, and which signs should prompt urgent review during a flare.