Why it is done:
This test is done to monitor the level of activity in Lupus as well as to aid in Lupus diagnosis.

How it is done:
This test requires a blood sample to be taken usually from the arm.

What is the Complement System:

What the test measures:
C3 and C4 are the most commonly measured complement compounds. CH50 and CH100 (total complement activity) will be measured if your doctor suspects deficiency that is not measured by C3 or C4.

How the test is used to monitor Lupus activity:
Since the complement system is used by the body to help clear immune complexes from the blood, it can be used to monitor activity in Lupus, particularly with glomerulonephritis and vasculitis.

Normal Levels:
Normal levels vary based on a number of factors including gender, age, and the lab doing the testing. Here is a basic guideline:
C3 - males: 88 to 252 mg/dl (880 to 2520 mg/L)
females: 88 to 206 mg/dl (880 to 2060 mg/L)
C4 - males: 12 to 72 mg/dl (120 to 720 mg/L)
females: 13 to 75 mg/dl (130 to 750 mg/L)

What Low levels mean: