Complement Blood Test
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A complement blood test measures the levels and/or activity of a group of proteins that are part of the complement system. This system 'complements' or enhances your body's defenses against infections and other diseases. Your immune system makes antibodies, which are proteins to fight disease-causing substances like viruses and bacteria.
The proteins in the complement system will also help fight the infection or disease. These proteins work together in a sequence, with one protein activating the next. 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 or a total complement test) measures the total activity and levels of all the major complement proteins.; If the CH50 level is not normal, each of the nine complement levels can be measured individually to find out which one is abnormal.; 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 health condition. If you have an autoimmune disease your immune system attacks the healthy cells of your organs and tissues by mistake.
Why this test is done
Your health care provider may order complement blood test if you have an autoimmune disease such as lupus. The test can show how well the treatment is working.
Your provider may also order this test if you have the symptoms of an autoimmune disease. The symptoms of autoimmune disease can depend on the part of your body that's affected. The symptoms can come and go and may include:
- Infections
- Unexplained inflammation, such as redness, swelling, heat and pain
- Fatigue
- Joint pain or swelling
- Muscle pain
How to prepare
You don't need any special preparations for a complement blood test.
Sample type
Blood
Other names for this test
complement antigen, compliment activity C3, C4, CH50, CH100, C1 C1q, C2, total complement test
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Educational content only. This entry describes what a test measures and how published reference ranges are defined. It is not a diagnosis, does not interpret your personal results, and is not a substitute for a qualified doctor.