How long do ulcerative colitis flare-ups last?

Flare ups of ulcerative colitis usually last for days or weeks and are unlikely to get better by themselves. Without treatment they can persist for longer, which can cause further damage to the lining of the colon. Ulcerative colitis tends to be a progressive condition which means that as time goes on, flare ups become more frequent and last for longer and periods of remission get shorter.