Ok don't quote me on this because I was pretty sick when the lab values were explained to me but if I understood it correctly and am remembering it right if both the C4 and C3 are low then it is almost 100% that you have Lupus if only one is low then it is not quite as indicative of lupus but still very possible. There are a lot of other things that contribute to the diagnosis. A lot of times they know you have an autoimmune disease but it can be hard for them to tell which one you have. They thought I had Crohns for 2 yr but it turned out I actually had Lupus. Sometimes they use how your body response to the medications to determine what you have. Sounds very annoying I know! You want it to be clear cut with a clear treatment plan. I hope they figure it all out for you. Not knowing is hard!

Hello c3&c4, here is what I found out tonight, There are nine protein groups of complement, so complement is identified by the letter C and the numbers 1 through 9. The most common complement tests for lupus are CH50, C3 and C4. CH50 measures the overall function of complement in the blood. Low levels of C3 or C4 may indicate active lupus.

I stay a anemic. During my knee surgery I had to have two pints of blood pump in me. I been that way since 1997. It is part of the disease. Remember.: You have a disease it doesn't have you. That is how I get through all this torment.

C3 & c4 involves blood work monthly, it measures during which time you are have had a flare. Example you just had blood work done and they include C3 & C4 to measure levels to see if you are having a flare or a decrease which means you are not having a flare.
If you would like more info look up on the Internet
NCBI Resources or type The complex nature of serum C3 and C4 as Bismark erst of lupus renal flare. It is the national library of medicines . Good luck it gives you high and low levels so you can comprehend lupus renal flare.

Thank you
Trina Rogers

Low c3 c4 are lab they run to screen for kidney or potential kidney issues. If you are low in one or both it MAY indicate present or future kidney issues. I have never had a low test and was still diagnosed. As far as I know it can be an indicator of many thing just not Lupus. They use it in many other illnesses to watch for certain things including some cancers.