The complement C3 test results vary depending on the person's health history, age, and sex. The normal range for the complement C3 test is 80 to 160 milligrams per deciliter or 0.8 to 1.6 grams per liter.
The complement levels in the blood rise after an injury or injection, but when the complement system responds to a disease, your complement levels go down.
High C3 complement levels indicate inflammation in the body. The inflammation could be due to ulcerative colitis or other acute diseases like sarcoma, leukemia, or Hodgkin's Lymphoma.
These are all different types of cancer. However, increased levels of C3 are not the main indication of cancer.
Elevated C3 complement levels are also observed in people with diabetes. Therefore, other tests are necessary to confirm the diagnosis.
Higher-than-normal levels of C3 proteins can indicate that you’ve just had an infection and your immune system is responding to it.
If you get treatment for a disease such as lupus, high levels of C3 indicate that the treatment works.
Increased C3 levels may also be a sign of:
- Heart attack (myocardial infarction) and other heart problems.
- Sarcoidosis (inflammatory disease).
- Thyroid disease
- Ulcerative colitis
If C3 values are abnormally high or low, additional tests or procedures may be ordered to narrow or confirm the suspected cause.
Interpretation of Low C3 Levels
Low C3 levels may be seen in conditions involving complement consumption, including active immune complex disease, septicemia, bacteremia, post-streptococcal glomerulonephritis, and disorders associated with nephritic factor.
When both C3 and C4 levels are low, this suggests activation of the classical complement pathway and is commonly associated with immune complex-mediated diseases such as active Systemic Lupus Erythematosus (SLE).
In contrast, low C3 with normal C4 suggests activation of the alternative complement pathway, which may occur in certain infections, alternative pathway complement disorders, or nephritic factor-associated disease.
Persistently low C3 levels can occur in some patients with longstanding SLE even without active disease. However, a sudden decline in C3 may indicate increased disease activity or flare, particularly when lupus nephritis is present or developing.
Measurements of serum complement components C3 is useful in the diagnosis and monitoring of immune complex disease e.g. SLE (Systemic lupus erythematosus) and some blood associated infectious diseases. Complement concentrations are acute phase proteins and may be normal, despite complement consumption, in some inflammatory and infective disorders. C3 alone is often decreased in infectious disease (septicaemia, endocarditis).
Measurement of serum complement is useful in the monitoring of specific immune complex diseases e.g SLE and infectious diseases post streptococcal disease, subacute bacterial endocarditis.
Complement C3
