C4 Complement Blood Test Results Fully Explained


Complement tests are ordered by medical providers in order to determine the presence of an abnormality or a deficiency within the complement system. It may be used to look at pathways or components that could be leading to disease development or a deteriorating condition. One of the most common forms of complement system testing is the C4 complement blood test result.

There are 3 common reasons why this blood test will be ordered.

1. To help with the diagnostic process of microbial infections that occur on a regular basis.
2. To help diagnose and/or monitor autoimmune diseases that may be acute or chronic in nature.
3. To help monitor complex-related conditions or diseases such as vasculitis.

A medical provider will order the C4 complement blood test when there is edema or inflammation of an unexplained nature.

What Is the Complement System?

The C4 complement blood test helps medical providers take a look at a person’s immune system. The complement system helps the immune system eliminate pathogens that may have invaded the body. C4 levels are just one of the complement measures that are looked at. C3, CH50, and CH100 blood tests may also be ordered for a complete look at the immune system to determine at least a guess as to what may be happening medically.

When To Speak With a Doctor

If someone has been to a medical provider several times within a short amount of time because of recurring bacterial infections, then a follow-up appointment for the C4 complement blood test is often a good idea. Any time there are symptoms that could be tracked to an autoimmune disorder is also a good time to speak with a doctor. Inflammation that occurs for some reason without explanation may also trigger this blood test order.

People who have certain symptoms of lupus should immediately approach their medical provider for this test. This includes mouth ulcers, hair loss, a butterfly rash across the checks, and unusual joint pain or swelling.

No preparation is usually necessary for this blood test to be completed. It can be drawn the same day that it is ordered.

Other tests may be ordered at the same time.

The C3 blood test is often ordered with the C4 complement blood test. All components from C1-C9 may be requested.

What Do My Test Results Mean?

The C4 complement blood test can be abnormally high or abnormally low. Most people, however, will have a test result that comes back as normal. If the test results show that there is a C4 deficiency, then it can mean there could be a number of potential health concerns present. The most common would be a bacterial infection. There may also be these additional health concerns based on an individualized medical history.

  • Liver disease or damage due to cirrhosis or hepatitis.
  • Ongoing malnutrition.
  • Autoimmune diseases or disorders, such as rheumatoid arthritis.
  • Several different types of kidney disease.

When there is an increased level of C4 in the blood test results, then this is generally an indication that there is inflammation happening somewhere within the body. This may be acute or chronic in nature. Increased complement activity may also be an indication of certain cancers, such as leukemia or Hodgkin’s lymphoma. Ulcerative colitis may also cause increased complement levels.

Having an increased or decreased C4 complement level cannot give a medical provider an idea of what is wrong with someone. It is simply an indication that a person’s immune system has activated for some reason.

Men and women have different levels that are considered to be normal. Men will have normal results if the test falls in the 12-72 mg/dL range. For women, the normal range is 75 mg/dL. Individual variability and laboratory differences may affect this range somewhat. A result that is slightly abnormal may or may not be medically significant.

The C4 Complement Blood Test Helps to Determine a Diagnosis

The C4 complement blood test is one tool of many that medical providers use to determine the status of a person’s health. If a specific test comes back with a deficiency or is abnormally high, then it is important to speak with a medical provider immediately. From alcohol abuse to kidney disease to chronic hepatitis, there are numerous options that a medical provider may look at.

Use this guide to ask questions about any specific results. This will help an effective treatment plan to be developed so that better health can potentially be achieved.