Complement C4



Quest Diagnostics Test Code: 353

Decreased C4 level is associated with acute systemic lupus erythematosus, glomerulonephritis, immune complex disease, cryoglobulinemia, congenital C4 deficiency and generalized autoimmune disease.

The complement system is a system made up of a handful of proteins that help to promote immune and inflammatory responses. It makes up part of the innate immune system. Complement proteins’ main role is to destroy pathogens like bacteria and viruses. Testing for complement measures their level in the blood which can point to diseases like autoimmune diseases. Complement component 4 (C4) is one of the complement proteins that activate the innate immune system. This test is commonly performed along with a complement C3 test to diagnose diseases like systemic lupus erythematosus, glomerulonephritis and other autoimmune diseases.

This test is performed in following conditions such as:

• Butterfly rash on the face
• Mouth ulcers
• Loss of hair
• Extreme tiredness
• Joint pain and swelling
• Pain in your chest when breathing deeply


Specimen Collected
  • Blood
Estimated Time Taken

Turnaround for this test is typically 1-3 business days.