Reviewed: 13. Juli 2026
C4 Complement C4
Unit: g/l
Quick Explanation
Complement factor C4, like C3, belongs to the complement system of immune defense. Low values are often measured together with C3 when autoimmune diseases like lupus are suspected, since both factors are often reduced with active disease.
📊 Reference Values
ℹ️ Reference ranges may vary slightly between laboratories. Always compare your value with the reference range from your own lab report.
🔍 Possible Causes
Value too high — possible causes
- ·Acute inflammation or infection
Value too low — possible causes
- ·Autoimmune diseases (e.g. systemic lupus erythematosus)
- ·Congenital complement deficiency
This list shows possible causes — not a diagnosis. Only your doctor can correctly interpret your result.
🩺 Questions for Your Doctor
- →What does my C4 value mean together with C3 and my symptoms?
- →Should a rheumatologist be consulted?
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Medical Disclaimer
The content on this page is for general information only and does not replace professional medical advice, diagnosis, or treatment. Always consult your doctor or pharmacist for health-related questions. Lab values should always be assessed in the context of your personal medical history.