What is Complement Component 3 (C3)

A Complement C3 test is a blood test that assesses how active a certain protein is.

The complement system uses this protein as a component. Over 60 proteins that are found in blood plasma or on the surface of certain cells make up the complement system. The proteins assist your immune system in preventing infections, removing dead cells, and removing foreign objects from your body.

Occasionally, few people may inherit a lack of certain complement proteins. They are more susceptible to autoimmune diseases or certain infections.

There are nine main complement proteins present. Their numbers range from C1 to C9.

Why is the Test Done?

The most often measured complement components are C3 and C4.

Those with autoimmune diseases may be monitored with a complement test. It is done to determine whether the condition's therapy is effective. Levels of complement proteins may decrease when the complement system is activated during inflammation. For instance, complement proteins C3 and C4 levels may be lower than usual in persons with active lupus erythematosus.

The test might also be conducted to check:

  • Fungal infections
  • Gram-negative septicemia
  • Parasitic infections, such as malaria
  • Paroxysmal nocturnal hemoglobinuria (PNH)
  • Shock

How is this test done?

For this test, blood is extracted from the veins. Most frequently, a vein from the back of the hand or the inside of the elbow is utilized.

The steps are as follows:

  • An antiseptic is used to clean the area.
  • The medical professional applies pressure to the spot and wraps an elastic band around the upper arm to cause the vein to expand with blood.
  • The medical professional carefully places a needle in the vein.
  • The blood gathers into a tube or vial that is linked to the needle and is sealed. You take off the elastic band from your arm.
  • The needle is taken out once the blood has been drawn. A cover is placed over the puncture site to halt any bleeding.

A sharp instrument called a lancet might be used to pierce the skin and induce bleeding in newborns or young children. The blood is collected onto a slide or test strip, a tiny glass tube known as a pipette, or both. If there is any bleeding, the area may be covered with a bandage.

How to prepare for the test?

For this test, no extra preparation is required. In case if any extra preparation is required, then your doctor will inform you beforehand.

What happens during the test?

Some patients experience significant pain when the needle is placed to draw blood. Some might just experience a stinging or prickling feeling. There can be some throbbing thereafter. But mostly goes in a very short span of time.

Understanding results

Regular Results

The regular range is 0.88 to 2.01 g/L (0.88 to 201 mg/dL, or milligrammes per deciliter).

Abnormal Results

Increased complement activity can indicate you might have:

Decreased complement activity may be seen in:

  • Bacterial infections (especially Neisseria)
  • Cirrhosis
  • Glomerulonephritis
  • Hepatitis
  • Hereditary angioedema
  • Kidney transplant rejection
  • Lupus nephritis
  • Malnutrition
  • Systemic lupus erythematosus
  • Rare inherited complement deficiencies

Important: Remember that various laboratories may have somewhat different normal value ranges. Ask your physician what your particular test findings signify.

The aforementioned illustrations highlight the typical metrics for these tests' outcomes. Different measures or specimens may be tested in some laboratories.


The modest risks of having blood collected include the following:

  • Excessive bleeding
  • Fainting
  • Dizziness Dizziness
  • Hematoma (blood accumulating under the skin)
  • Infection (a minor possibility each time the skin is damaged) (a slight risk any time the skin is broken).


In the blood, a sequence of events is known as the complement cascade. The complement proteins are activated by the cascade. The end product is an attack unit that punctures bacteria's membranes and kills them. C3 binds to germs and destroys them there.

Frequently Asked Questions

1. What does Complement C3 mean?

A test for C3 complement tells about the immune system. It displays how certain immune system components react to noxious chemicals. Your doctor can use this test to identify other problems and autoimmune diseases (like lupus).

2. What does a C3 test with a high Complement mean?

Higher levels of the C3 Complement indicate inflammation within the body. Ulcerative colitis or other acute illnesses, including sarcoma, leukemia, or Hodgkin's lymphoma, may be to blame for the inflammation.

3. Why do C3 levels drop?

C3 levels decrease due to conditions like acute glomerulonephritis, membranoproliferative glomerulonephritis, immunological complex illness, active systemic lupus erythematosus, septic shock, and end-stage liver disease.

4. What is C3 Complement deficiency?

Complement component 3 deficiency is very rare, inherited primary immunodeficiency characterised by a potential for infection (mostly by gram-negative bacteria) as a result of abnormally low plasma levels of C3.

5. What is the normal range for C3?

The normal range for C3 is 88 to 201 milligrams per deciliter (mg/dL) (0.88 to 2.01 g/L).

6. What are the symptoms of C3 deficiency?

The symptoms of C3 deficiency are recurrent episodes of sinusitis, tonsillitis, otitis, upper and lower respiratory tract infections, pneumonia, and skin infections.

7. What disease can cause a high Complement level?

Conditions that cause high complement level are certain types of cancer, leukemia, non-Hodgkin lymphoma, and ulcerative colitis.

8. Is the C3 test done on an empty stomach?

The complement C3 test requires 10-12 hours of fasting (Overnight Fasting) is suggested.

9. What is the Complement C3 Test cost?

Complement C3 Test cost starts from Rs. 500 approximately however, it can vary due to many factors.

10. Where can I get the Complement C3 Test ?

If you are looking for a Complement C3 Test, then visit Medicover Hospitals, it offers various diagnostic tests.