All Tests

A complement test is a blood test that measures the activity of a group of proteins in the part of the blood called the serum. These proteins make up the complement system, which is part of the immune system.

The complement system helps antibodies fight off infections and destroy substances that are foreign to the body, such as viruses, bacteria, and other germs. It’s also activated when the body makes antibodies against its own tissues that it views as foreign. This happens in autoimmune diseases.

A complement test can monitor the progress of people undergoing treatment for autoimmune diseases, such as lupus and rheumatoid arthritis (RA). The test can measure how advanced these diseases are based on the activity of the complement protein in the blood. It can also gauge the effectiveness of ongoing treatments for autoimmune disorders and diagnose some cancers and infectious diseases.

There are nine major complement proteins. They’re labeled C1 through C9. A total complement measurement checks the function of your complement system by gauging the total amount of complement protein in your blood.

The complement test involves a simple blood draw. It requires no preparation and carries few risks. Your doctor will send the blood sample to a laboratory for analysis. Your doctor will receive the results.

> or =16 years: 30-75 U/mL

Reference values have not been established for patients that are <16 years of age.