What is a complement blood test?
A complement blood test measures the amount or activity of complement proteins in the blood. Complement proteins are part of the complement system. This system is made up of a group of proteins that work with the immune system to identify and fight disease-causing substances like viruses and bacteria.
There are nine major complement proteins. They are labeled C1 through C9. Complement proteins may be measured individually or together. C3 and C4 proteins are the most commonly tested individual complement proteins. A CH50 test (sometimes called CH100) measures the amount and activity of all the major complement proteins.
If the test shows that your complement protein levels are not normal or that the proteins aren't working with the immune system as well as they should, it can be a sign of an autoimmune disease or other serious health problem.
Other names: complement antigen, compliment activity C3, C4, CH50, CH100, C1 C1q, C2
