Complement C3 Blood Test

The complement system is a group of proteins that are important for your protection against infection and play a role in inflammation development.

There are nine major complement proteins. They are labeled C1 through C9. Complement C3 is the most important and plentiful protein in the complement system. These different components travel through your bloodstream to find foreign invaders like bacteria or viruses. When this happens, the complement system is activated and functions as a cascading event such as the fall of a series of dominos. Most of the time, the result of complement activation is favorable; the "foreign invader "is removed without cell or tissue damage. However, the activation of the complement system in some people becomes uncontrolled, or certain components may be deficient causing the risk of recurrent mild or serious bacterial infections or autoimmune disease.

A number of conditions, such as increased bacterial infections, rheumatoid arthritis, cirrhosis, hepatitis, kidney disease, malnutrition, and septicemia, are associated with lower than normal complement levels. Increased complement levels may be associated with acute or chronic inflammation or cancer, ulcerative colitis or thyroiditis.