Does all insurances cover ulcerative colitis, since it's chronic?

You'd think so, but-: Insurance companies have differing rules. Many won't cover "pre-existing conditions", meaning something that was diagnosed before you tried to get coverage. If you had uc diagnosed, and later tried to obtain health insurance from a new carrier, the carrier may well deny coverage for any treatment related to the uc. That's one of the reasons that "portable" health insurance is a good idea.

Most do: Some companies have pre-existing conditions, but the laws have been helping that go away. You should check with your insurance company to be sure.