COMPLEMENT C3, SERUM

Complement C3, Serum

What it is

The Complement C3, Serum test measures the level of complement component 3 (C3) in the blood. C3 is one of the most important proteins in the complement system, a part of the immune system that helps fight infections, clear damaged cells, and trigger inflammation when necessary.

Uses

This test is commonly used to evaluate immune function and diagnose conditions involving abnormal immune activity. It is particularly important in the diagnosis and monitoring of autoimmune diseases such as systemic lupus erythematosus (SLE) and certain types of glomerulonephritis (kidney inflammation). It may also be used to assess recurrent infections or to evaluate overall complement activity along with C4 and CH50 tests.

Symptoms That May Lead to the Test

Doctors may order this test if you experience symptoms such as joint pain and swelling, persistent skin rashes (such as the butterfly rash of lupus), unexplained fevers, fatigue, swelling in the legs, foamy urine, or recurrent bacterial infections. These symptoms may suggest autoimmune or kidney-related disorders.

Abnormal Results

Low C3 Levels: May indicate autoimmune disease (like lupus), certain kidney diseases (e.g., post-streptococcal glomerulonephritis), severe infections, or rare hereditary complement deficiencies.

High C3 Levels: Can be seen in acute inflammation, infections, metabolic syndrome, obesity, or diabetes, reflecting increased immune activity.

Normal Levels: Suggest no significant abnormalities in complement C3, though further immune tests may be required depending on clinical suspicion.

Risks

The test requires a simple blood draw. Risks are minimal and include mild pain, slight bruising, or temporary dizziness at the puncture site. These side effects are minor and usually resolve quickly.