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Complement C4

C4 Complement Component 4
Serum (SST) g/L

About this test

Complement protein of the classical and lectin pathways. Genetically low C4 levels occur in C4A null alleles (associated with SLE susceptibility).

Reference Ranges

Sex Age Range Notes
All ≥ 18 yrs 0.16 – 0.38 Adult

Clinical Interpretation

Low / Decreased
SLE (especially active nephritis), hereditary angioedema (C4 low during and between attacks), C4 null allele.
High / Increased
Acute-phase reactant.

Related Tests

Anti-dsDNA Complement C3
Specimen
Serum (SST)
Reporting Unit
g/L
Category
🛡️ Immunology

⚠ Clinical Note
Reference ranges are indicative. Always interpret results in the context of the individual patient and local laboratory reference intervals, which may vary.