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Complement C2 Blood Test

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The Complement C2 Blood Test measures C2 levels in the blood to help diagnose a deficiency.


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Test Code:


CPT Code(s):


Also Known As:

C2 Complement


Immunologic Quantitation by Radial Immunodiffusion (RID)




No special preparation is required.

Test Results:

5-6 days. May take longer based on weather, holiday, or lab delays.

Walk-In Lab is prohibited from selling LabCorp tests to residents in the following states:NY, NJ, RI, MA, MD

What is the purpose of this test?

Order this Complement C2 Blood Test, which measures C2 levels in the blood to help diagnose a C2 deficiency. C2 is a component of the complement system, a part of the body’s innate immune system. The Complement C2 Serum Test, or simply C2 Blood Test, is ordered to detect and diagnose a deficiency of C2 that could be associated with immune complex and rheumatic diseases. C2 deficiency, hereditary or acquired, is the most common complement deficiency.


What conditions cause abnormal C2 levels?

Several underlying health conditions may result in abnormal C2 levels; therefore, it is vital to use screening tests such as this to help determine the cause. Underlying health conditions associated with a C2 deficiency include:


  • Discoid lupus erythematosus (DLE) or systemic lupus erythematosus (SLE)
  • Vasculitis - inflammation of the blood vessels
  • Dermatomyositis - inflammation of the muscles and skin
  • Glomerulonephritis - inflammation of the kidneys’ filters
  • Atrophoderma - skin atrophy
  • Cold urticaria - allergy to cold temperatures resulting in skin inflammation
  • Inflammatory bowel disease (IBD)
  • Recurrent infections


However, it is essential to note that not all patients with a C2 deficiency will develop such conditions.


When should I order a Complement C2 Blood Test?

Individuals may order a Complement C2 Blood Test if they have symptoms of a C2 deficiency or an autoimmune disorder, especially lupus. Symptoms of a deficiency or autoimmune disorder may include:


  • A butterfly-shaped rash across the nose and cheeks
  • Fatigue
  • Mouth sores
  • Hair loss
  • Sensitivity to sunlight
  • Swollen lymph nodes
  • Chest pain when breathing deeply
  • Joint pain
  • Fever


In addition, individuals may also order this test if they are undergoing treatment for lupus or other autoimmune disorders. This test can help monitor how well the treatment is working. For more information about the complement system, see details on the CH50 Blood Test page. Walk-In Lab also offers  C1q Blood Test and C4 Blood Test.

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