C3 Complement Blood Test

What is a C3 complement blood test?

A C3 complement blood test measures the levels of a specific type of protein in your blood (C3 proteins). C3 proteins are part of your complement system, which is connected to your immune system. C3 proteins destroy organisms that make you sick and they help heal your body after an illness. But sometimes, C3 proteins launch an attack against healthy cells by mistake.

The results of this blood test give your healthcare provider information about how your immune system is working. By measuring the amount of C3 proteins, your healthcare provider can diagnose infection, disease, immune deficiency and other health conditions, like autoimmune disorders. This test also helps your healthcare provider monitor treatment for certain autoimmune diseases.

When is a C3 complement blood test performed?

Your healthcare provider may order this test if you have:

• Bacterial infections that don’t go away or keep coming back.
• Edema (swelling) or inflammation.
• Symptoms of an autoimmune disorder, like lupus.

Your healthcare provider might also recommend a C3 complement blood test to monitor:

• Immune complex-related conditions, including glomerulonephritis (GN) and vasculitis.
• Treatments for autoimmune disorders, including lupus or rheumatoid arthritis (RA).

How does a C3 complement test work?

Your healthcare provider removes a sample of your blood through a vein in your arm. It takes just a few minutes. Then, they send the sample to a lab to check the levels of C3 proteins in your blood.

The lab may also look at the levels of other proteins (such as C4 proteins) and see how they compare to the amount of C3 proteins. Your healthcare provider will contact you when the results are ready and explain what they mean.

What should I expect during a C3 complement test?

You don’t need to do anything to prepare for a C3 complement blood test. Here’s how you can expect a C3 test to go:

1. A phlebotomist will wrap an elastic band around your elbow to locate a vein in your inner arm or hand.
2. They clean the area with antiseptic.
3. They insert a needle into the vein. You may feel a sting or pinch from the needle.
4. Your provider collects a sample of your blood in a tube.
5. They remove the needle.
6. Your healthcare provider will tape some gauze to your arm where the needle was.

What should I expect after a C3 complement test?

Your arm may be sore for several hours, and you may get a small bruise on your vein.

What are the risks of a C3 complement test?

Blood tests are very safe, and they give your healthcare provider important information. There aren’t any risks of a C3 blood test. If you don’t like having to give a blood sample or feel faint after giving blood, let the phlebotomist know.