Pathology Handbook

C4 Complement

Clinical Indications

C4 is usually measured in investigation of patients with renal disease, joint disease and multi-system disorders with evidence of vasculitis; low concentrations imply an immunological basis for the symptoms. C4 (and C3) levels may be useful in patients with recurrent infections with normal or raised immunoglobulin levels, since genetic and acquired defects sometimes present as immunodeficiency (CH50 analysis also required in such cases).

Request Form

Request on ICE


On request

Specific Criteria

Investigation of genetic or acquired complement defects or if agreed with Consultant Biochemist.

Turnaround Time

5 days




2 ml


Vacutainer gold top

Causes for Rejection

Unlabelled or incorrectly labelled sample; not meeting specific criteria for analysis.

Reference Range

0.14 - 0.54 g/L