COMPLEMENT C4 IS A BLOOD TEST THAT MEASURES THE ACTIVITY OF A CERTAIN PROTEIN. C3 AND C4 COMPLEMENT IS PARTS OF A GROUP OF GLOBULIN PROTEINS FOUND IN THE BLOOD.
PROTEINS C3 AND C4 ARE THE MAIN TWO. COMPLEMENT ACTIVITY MAY BE MEASURED TO DETERMINE HOW SEVER A DISEASE IS OR IF TREATMENT IS WORKING, ALSO THESE TEST MAY BE USED TO MONITOR PATIENTS WITH AN AUTOIMMUNE