Should I see a rheumatologist if I have elevated complement levels?

Don t think so. Complement is an acute phase reactantant , having high complement levels only means there is a reaction , probably inflammatory . If the diagnosis is ulcerative colitis , but you don t have arthritis youndont need to see the rheumatologist for high complement leves.
No. See your PCP. Elevated complement levels are seen in some infections, some cancers, and in ulcerative colitis. The first two are conditions not necessarily treated by rheumatologists. Depending on the reason for your elevated complement and the symptoms that prompted the test you may benefit from additional blood tests and/or body scans. I suggest starting with a discussion with your primary care provider.
Probably. Complement levels are very nonspecific but can be elevated with conditions like lupus. You can get an opinion from a rheumatologist.