Test Overview
Test Methodology


Test Usage

Quantitation of C3 is used to detect individuals with inborn deficiency of this factor or those with immunologic disease in whom complement is consumed at an increased rate. Increased levels are found in numerous inflammatory conditions as an acute phase reactant. Acquired deficiency is encountered in active lupus and glomerulonephritis. May be decreased in immune complex disease, serum sickness, chronic active hepatitis, inborn C3 deficiency and subacute bacterial endocarditis (SBE).

Reference Range *

Adult: 83-240 mg/dl

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

Detects both biologically active and inactive C3.

Test Details
Days Set Up
Daily, 24 hrs
Analytic Time

2 hours

Soft Order Code
MiChart Code
C3 Complement
  • C3
  • B1C/B1A
  • C3
  • Complement C3
  • Third Component of Complement
Chemical Pathology
Specimen Requirements
Collection Instructions

Collect specimen in an SST tube. Centrifuge, aliquot serum into a plastic vial and refrigerate up to 8 days or freeze for longer storage.

Alternate Specimen
Red top tube, Green top tube (heparin). [rev 8/03]
Normal Volume
0.5 mL serum
Minimum Volume
0.25 mL serum
Rejection Criteria
Lipemic serum
Additional Information

C3 comprises about 70% of the complement system and is utilized in both the classical and alternate pathways of complement activation. Increased levels are found in numerous inflammatory states as an acute phase reactant. CH50 (total complement hemolytic activity), C3 and/or C4 may be decreased in cases of systemic lupus erythematosus, especially in cases with lupus nephritis, in acute and chronic hypocomplementemic nephritis, SBE, disseminated intravascular coagulation (DIC), and partial lipodystrophy (with associated nephritis-like activity in serum). Cases of hereditary C3 deficiency, while rare, have been reported and are characterized clinically by recurrent infections (e.g., pneumonia, meningitis, impetigo). Low C3 levels have also been found in cases of uremia, chronic liver diseases, anorexia nervosa, and coeliac disease.

CPT Code
Fee Code