blood tests that measure the activity of a certain protein that is part of the complement system. The complement system is a group of proteins that move freely through your bloodstream. The proteins work with your immune system and play a role in the development of inflammation. Higher than normal levels can mean different things and this should be discussed with your physician who ordered the tests.
In general, elevated levels may direct your physician to evaluate your further for possibility of some type of infection which may be present. Hope this helps!