Immune system of human body contains proteins called complement. The complement varies from C1 to C9. When a person faces auto immunity disorder, it is necessary to check the regularity of C4 complement proteins. C3 and C4 complements has major role in immune system. A normal human body must contain 0.16 to 0.48 grams of C4 in 1 liter of blood (g/l). Human body shows symptoms when this average disturbed. The average may be different based on age, height and gender. Physician suggests this test when a patient encounters fatigue, puffiness around eyes, Rashes across chin (mostly butterfly shaped rash), swelling in hands and feet, and excessive tiredness.