Complement C4 Blood Test
Complement C4 is a blood test which measures a certain protein's activity. This protein is part of the complement system. The complement system is a protein group that circulates freely through your bloodstream. The proteins work with your immune system and play a role in inflammation development. The complement system protects the body from infections, dead cells, and foreign material.
The complement C4 test is one of the most widely used complement tests. This test is useful to individuals who experience symptoms typically indicative of an autoimmune disease, especially lupus. These symptoms may include:
- muscle pain
- muscle weakness
- muscle paralysis
- extreme fatigue
- sudden, unexpected weight loss
- joint pain
The complement C4 test is also sometimes used to monitor protein levels in people with autoimmune disease. Complement tests can provide valuable information on the efficacy of current autoimmune treatment. If you are treated for a disease such as lupus and your complement C4 level increases, it can be a sign that your treatment is working.
Your complement levels often dramatically increase immediately after an infection or injury. When your complement system is activated in response to ongoing diseases such as lupus, the levels generally decrease.
You can inherit a deficiency in your complement C4, but an acquired deficiency is much more common. If only your C4 complement level is low and all other components are normal, it is usually due to a hereditary component deficiency.
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