C3 / C4
Immune system proteins consumed during certain autoimmune flares.
What is it
Complement C3 and C4 are proteins of the immune system's complement cascade. Levels can be consumed (lowered) during active autoimmune disease.
Why it's measured
Low C3 and C4 have been associated with active lupus and certain other autoimmune conditions in published research.
Reference range
Standard laboratory reference
C3: 90 – 180 / C4: 10 – 40 mg/dL
Reference ranges vary by laboratory. Your individual reference range will appear on your test report and should be interpreted by your physician in the context of your overall health profile.
What results may indicate
Elevated
May reflect inflammation in research literature.
Lower
Has been associated with active autoimmune disease, particularly lupus flares.
These associations are general. They are not a personal diagnosis or prediction. Discuss your individual results with your physician in the context of your full health profile.
When it's measured
Used in evaluating autoimmune disease activity, especially lupus.
Related markers
Measured in
A complete look at your heart, hormones, metabolism, inflammation, and longevity systems — drawn at Quest or LabCorp, reviewed by a U.S.-licensed physician.
Explore the Apex Panel →This information is for general educational purposes only and is not medical advice. Lab results alone are not intended to diagnose, treat, or cure any condition and do not replace the advice of a healthcare provider. OPTML does not offer medical advice, a diagnosis, medical treatment, or any form of medical opinion.