Overview:
The Complement 4 (C4) test measures the level of the C4 protein, a part of the complement system involved in immune response and inflammation. It helps evaluate immune system function and detect complement deficiencies or overactivation.

Risk Assessment:

• Generally, the test is safe with minimal risk as it requires only a blood sample.

• Risks include slight pain, bruising, or infection at the blood draw site, which are rare.

Normal Range:

• Typically, 10-40 mg/dL (may vary by laboratory; always refer to local lab reference values).

Interpretation:

• Low C4 levels may indicate:

  • Autoimmune diseases (e.g., lupus erythematosus)

  • Complement consumption in infections or inflammation

  • Hereditary angioedema

• High C4 levels are less common and may occur during acute inflammation or infection.

Sample Type:

• Blood sample collected via venipuncture (serum or plasma depending on lab requirements).