The C3 Test: What You Need to Know About Complement Levels?

A C3 test is a blood test that determines the health of your immunity system. With this test, the medical experts will determine how different parts of your body’s immune system respond to harmful substances. A C3 complement test helps your doctors identify the presence of any autoimmune disorders or other health conditions.

This article explains everything associated with the C3 test and its complement levels. So, read along till the end!

What is a C3 Complement Test?

With this blood test, the doctors will determine the levels of C3 protein in your blood. These C3 proteins play a major role in destroying the germs or microbes possibly responsible for making you sick. At times, when these proteins attack the healthy cells by mistake, such a condition triggers autoimmune disorders.

The test helps to assess the proper functioning of the immune system by measuring the amount of C3 proteins in your body. The medical expert will diagnose diseases, infections, weakened immunity and other conditions.

What is the Meaning of the Complement System in this Test?

C3 proteins fall under the category of the complement system, which is one of the many parts of your immunity system. There are more than thirty different proteins within the complement system. All of these proteins work together to protect you from illness or infections.

Every time your immune system detects any harmful substance, such as a virus, bacteria or infection in your body, it activates a specific protein within your complement system. This protein is responsible for initiating an attack against the harmful substance. This protein activates another of its kind from the complement system, and they keep activating one another like a chain reaction.

Healthcare providers call this natural function of the immunity system the complement cascade. In such a process of your immunity system, the C3 proteins are consumed to heal your body from the adverse virus, bacteria or infections.

Role of Complement System Within Your Body

The role of the complement system within your body includes the following:

  • Helping the body eliminate all dead cells and other associated wastes
  • Assisting the immune system in making more antibodies or proteins to respond to specific substances.
  • Making the antibodies effective and powerful in overpowering the harmful substances
  • Neutralizing and preventing the viruses from causing more damage to the internal functions of your body
  • Working with other associated body parts to kill the bacteria

C3 test is a specific examination for determining the levels of this protein in your complement system. When this protein is deficient in your immune system, then the possibility of certain infections or health disorders increases. It means that your complement system cannot supply enough C3s to the immune system to fight off bacteria, viruses or other harmful substances.

When Should You Seek Getting a C3 Complement Blood Test?

When you visit your doctor to get some adverse symptoms treated, he/she might diagnose you with some bacterial or viral infections. They will give you medications to weaken the bacteria or virus, whereas the immunity system will take care of it. If the symptoms persist, and the infection and its associated symptoms keep coming back, then the doctor might recommend a C3 test on priority.

Apart from that, autoimmune disorders such as lupus, inflammation, and other conditions might also initiate the need for you to seek a C3 complement test.

Understanding the C3 Complement Test Results

The result of the C3 complement test varies, depending on a person’s age, sex and health history. The normal or healthy range of the complement levels is in the range of 80 to 160 mg/decilitre.

The complement levels increase when your body experiences an injury, but when it fights a disease, the levels decrease.

Low C3 Complement Levels: If the complement components within your body are normal, but the C3 levels are low, then you have a C3 component deficiency. This might trigger some forms of autoimmune diseases in your body. If the test result shows low levels of other associated complement proteins, this might be due to some acquired disease. You should know that low C4 and C3 might result in an autoimmune disorder, lupus. Some of the other acquired health conditions which reduce the complement protein levels in your body include malnutrition, hepatitis, bacterial infections, cirrhosis and others.

High C3 Complement Levels: If the C3 protein levels are high in your complement system, it determines inflammation within your body. It might be due to health conditions such as leukaemia, lymphoma, and ulcerative colitis. Even though these are some forms of cancer, the increased C3 levels don’t indicate it as a priority. The rise of C3 levels is also a problem in people with diabetes.


This is everything that you must know about the C3 test and the complement levels. If you are experiencing any form of a bacterial infection or health disorder that should heal over time but is persistent and keeps returning, you should get a C3 test or complement system test done immediately for a better diagnosis.

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