How can you die for ulcerative colitis?

NO If you take care : Ulcerative colitis most of the time could be controlled , with aim of prolonged remission, possible to prevent most of complications , need to be followed by a professional team ( doctors ) negligence , or delay in seeing professional help could be lethal , as complications like toxic megacolon , perforation , malignancy etc are part of this treacherous disease

Rare: As stated already, it's actually rare to die directly from uc. The main cause of death that can be tied to uc would be cancer. Many decades of inflammation can lead to bowel cancers. Also, medications from uc are associated with a risk of lymphoma. Even if you get cancer, it may not cause death. Some of these cancers are treatable with chemotherapy, radiation, and surgery.