What is complement C4?

Frequently Asked Questions:

Why do I need the complement C4 test?

A doctor may recommend the complement C4 test if a patient shows symptoms that indicate an injury, a recent infection, or an autoimmune disorder. These could range from muscle pain, frequent joint aches, headaches, extreme fatigue affecting daily chores, swelling of any form, hair loss, swollen lymph nodes, anemia, muscle paralysis, or unexplained weight loss.

What happens during a complement C4 test?

A complement C4 test is a medical procedure where a healthcare provider draws blood from a patient's vein. The process involves tying an elastic band around the upper arm to make the veins more accessible, cleansing the chosen area with an antiseptic to ensure it's sterile, inserting a small needle into the vein to collect a blood sample, and then applying a bandage to the puncture site. This blood sample is then sent to a laboratory for analysis. The purpose of this test is to measure complement C4 levels in the blood, aiding in the evaluation of the immune system and the detection of certain medical conditions.

What is the normal range for the complement C4 test?

Worldwide, 16 to 48 milligrams per deciliter (mg/dL) or 0.16 to 0.48 grams per liter (g/l) is the normal range for the test results. This marker may vary slightly from laboratory to laboratory. It is necessary to connect with a doctor to understand the specific meaning of the test results for further treatment.

What does it mean if your complement C4 is high?

An inflated or elevated C4 level may indicate a recent injury or infection that has taken place. The increased activity of C4 proteins in the bloodstream may also indicate certain complex conditions such as cancer (leukemia or non-Hodgkin lymphoma) and a gastrointestinal disease known as ulcerative colitis. Seeking the advice of a doctor is recommended.

What causes lower C4 levels?

Lower-than-normal C4 levels indicate a range of conditions in a patient. It could be a sign of autoimmune disorders such as lupus or rheumatoid arthritis, lupus nephritis, cirrhosis, bacterial infection, malnutrition, hepatitis, hereditary angioedema, chronic kidney or liver conditions, rare inherited complement deficiencies, or even kidney transplant rejection.  A doctor will usually recommend other tests for further evaluation.

What does the C4 complement test for?

The complement component 4 test helps a medical practitioner better understand how a patient’s immune system responds. The C4 is an essential protein to ward off harmful invaders such as viruses, bacteria, foreign substances, and dead cells. This blood test acts as an inflammatory marker to diagnose an infection, chronic illness, or autoimmune disorder.

Are there any preparations needed before taking the test?

Since the complement C4 is a straightforward procedure, no preparations are necessary. A healthcare professional simply draws blood from the vein at the back of the arm and sends it to the sample for testing. Most people do not see any side effects of having blood drawn. Some minor risks include excessive bleeding, lightheadedness, or soreness.

Why is C4 low in lupus?

When a patient is diagnosed with lupus (an autoimmune condition), his/her body suffers from an impaired or altered immune system response. The clear indicator of this is lower C4 and C4 levels in the body. A doctor may recommend this test at regular intervals to check the progress and see how the body responds to treatment.