C4 is used to measure protiens in the kidney. Here is a site I use to locate information when I have questions on my blood work. They had some good info on C4 as well. I just type the test in the search category. http://www.hss.edu/conditions_14346.asp
Test: Complement, CH50, C3, C4 - Complement is a series of proteins that help antibodies fight antigens: CH50 refers to the amount of complement necessary to destroy 50% of red blood cells in an immune reaction. C3 and C4 are the third and fourth components of the complement proteins.
What test is for: Complement is used up in immune reactions such as lupus.
What a positive test means: Low levels of complement mean the body is undergoing a severe immune reaction, primarily in the kidneys. Lupus is one cause, but there are many others. CH50 is usually 150-300 units. C3 is about
80-150 mg/dL. C4 is about
What a negative test means: Normal levels of complement make lupus inflammatory kidney disease unlikely. Other types of kidney disease, such as leaky kidneys or scarring, can still occur even if complement is normal. Other types of lupus do not usually lower complement.
Lupus - 1997 Fibro - 2001 Sjorens - 2007 Raynauds - 2008
Plaquenil, Imuran, Prednisone, Synthroid, Topomax, Effexor, Norco, Prilsec, Xanex, Elidel, Restasis