The symptoms of ulcerative colitis develop little by little. They can be continuous or recur every few weeks or months with long symptom-free periods (remission) in between.

A typical symptom is bloody diarrhea and cramping abdominal pain before defecation, lasting for several weeks or recurring. In proctitis there is not always diarrhea, but the bowel works more often than normally and there is blood in the stools. As the bloody diarrhea continues, anemia and fatigue develop, but fever is uncommon, unless the illness is already severe. In children, growth may be delayed.

Already in an early phase, sometimes even before bowel symptoms, joint, skin or eye symptoms may be present.