How can we help?

Home

C3 & C4 Complement Panel

Also referred as

Compliment activity C3 & C4

C3 and C4 complement test

C3 & C4 blood test

Total Complement

308+ booked recently

For men & women

Earliest reports in

18 hours

Contains

2 tests

Know more about this test

The C3 & C4 Complement Panel measures the levels of complement proteins C3 and C4 in the blood. It helps diagnose and monitor autoimmune disorders, infections, and other conditions affecting the immune system.

Samples required

Blood

Find out

Why is this test booked?

Preparations

Overnight fasting required for 8 to 12 hours

Sample Collection

Who will collect your samples?

Understanding C3 & C4 Complement Panel

The Complement proteins C3 and C4 are the integral components of the immune system. These proteins work together to enhance the ability of antibodies and phagocytic cells to clear pathogens. The C3 & C4 Complement Panel helps diagnose and monitor autoimmune diseases like systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and immune-related conditions.

Consider getting tested with the C3 & C4 Complement Panel if you have symptoms suggestive of autoimmune diseases, such as unexplained inflammation, frequent infections, chronic fatigue, joint pain, skin rashes, etc. Also, it can be done when there are risk factors such as family history of autoimmune disorders. Additionally, this panel may be advised if other tests indicate impaired immune function or as a part of a comprehensive evaluation for a condition with unexplained inflammation.

The C3 & C4 Complement Panel helps differentiate between various types of immune system dysfunctions, monitor disease activity, and assess the effectiveness of treatments. It also helps identify potential complications related to abnormal complement activity, guiding doctors to tailor appropriate therapeutic strategies.

Increased levels of C3 and C4 complement proteins are seen in acute phase response, inflammation, infection, injury, biliary obstruction, focal glomerulosclerosis, skin conditions such as psoriasis, dermatitis, hives, ulcerative colitis, Crohn’s disease, psoriatic arthritis, rheumatoid arthritis, rheumatic fever, and kidney failure. Decreased levels are seen in infancy, genetic deficiency, acquired deficiency like lupus nephritis, collagen vascular diseases, severe infections, alcoholic liver disease, and hereditary or acquired angioedema.

An overnight (8-12 hours) fasting is preferred for the C3 & C4 Complement Panel. Inform your doctor about any medications or supplements that you may be taking and any existing health conditions, as all these factors may potentially influence the test results.

Lab test results may vary across different laboratories. Abnormal test results require expert interpretation; therefore, never try to self-medicate based solely on these results, and always consult a doctor for a proper understanding of the test results. Insights from this test help the doctor tailor an appropriate treatment plan.

What does C3 & C4 Complement Panel measure?

Contains 2 tests

The C3 & C4 Complement Panel measures the levels of complement proteins C3 and C4 in the blood. These proteins play an important role in the body’s defense against infections by helping to clear pathogens and damaged cells. The complement system works in sync with antibodies and other parts of the immune system to fight off infections and facilitates the removal of dead or damaged cells. Measuring the levels of C3 and C4 proteins can provide important insights into the immune system's activity and health. Low levels of these proteins may indicate the presence of autoimmune diseases, such as systemic lupus erythematosus (SLE), where the body's immune system mistakenly attacks its own tissues. On the other hand, abnormal levels can also be associated with chronic infections, inflammatory conditions, or immune deficiencies. This test is often used in conjunction with other diagnostic tests to provide a comprehensive view of the immune system's function and to help doctors diagnose and monitor conditions affecting the immune system.

Frequently booked together

FAQs related to C3 & C4 Complement Panel

What is the C3 & C4 Complement Panel?

The C3 & C4 Complement Panel is a blood test that measures the levels of complement proteins C3 and C4. These proteins play crucial roles in the immune system by helping to clear pathogens and damaged cells. The test helps evaluate the activity and integrity of the complement system.

Why is the C3 and C4 complement test ordered?

The C3 and C4 complement test is ordered to diagnose and monitor autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis, as well as to assess the presence of complement deficiencies. It can also help in evaluating unexplained inflammation or infections.

How is the C3 and C4 complement test performed?

A phlebotomist (a trained professional to perform blood draws) will clean your skin using an antiseptic alcohol cotton swab or wipe and take blood samples from your vein using a needle. The blood sample will be stored safely and transported to the laboratory for analysis.

How should I prepare for the C3 & C4 Complement Panel?

Generally an overnight fasting is preferred before undertaking the C3 & C4 Complement Panel.

Are there any risks associated with the C3 & C4 Complement Panel?

No, the C3 & C4 Complement Panel is generally safe with minimal risks. However, you may feel slight discomfort during blood sample collection but chances of serious complications are extremely rare.

What do high levels of C3 and C4 mean?

High levels of C3 and C4 are less common but may be seen in acute inflammation or infection. Elevated C3 can occur during an acute phase response, while high C4 levels might be observed in certain inflammatory conditions.

How do C3 and C4 levels relate to immune system function?

Both C3 and C4 levels provide insights into immune system activity. Low levels of these proteins can indicate autoimmune diseases or a genetic deficiency, while high levels might be seen in acute inflammation or infection.

What is the difference between C3 and C4?

C3 and C4 tests measure the levels of these specific proteins in the blood. While both tests assess complement activity, C3 is often more broadly indicative of complement system function, whereas C4 levels are particularly relevant in the context of the classical pathway and autoimmune conditions.

In which conditions might C3 levels be abnormal?

Low C3 levels are often associated with systemic lupus erythematosus (SLE), certain kidney diseases, and other autoimmune disorders. High C3 levels can be seen in acute inflammatory states or infections.

In which conditions might C4 levels be abnormal?

Low C4 levels are commonly observed in SLE and other autoimmune diseases. High C4 levels are less common but can occur in some inflammatory conditions.

Can both C3 and C4 levels be low simultaneously?

Yes, both C3 and C4 levels can be low simultaneously, particularly in conditions like active systemic lupus erythematosus (SLE), where there is increased utilization of these proteins due to immune complex formation and inflammation.

Content created by

Dr. Swati Gupta (Anand)

MBBS, MD Lab Medicine

Want to know moreRead our editorial policy

Last Updated

10th Oct 2025