@TrixieStix Am hoping this is the right place to post this and I know we've been talking about C3 and C4 levels in a few threads (and we can continue to chat via PM, too). It turns out that I was tested for C3 and C4 levels in early May 2016 by a rheumy who was ultimately unable to help me. My levels were low but were within range at that time. I have no idea what they are now almost a year later. My C3 was "95" and range was 87-200 and my C4 was "21" and range was 19-52. Those same tests showed I had a positive ANA of 1:160, speckled pattern, and that I had the two Hashimoto's autoantibodies (which I already knew). My other tests (not done by the rheumy) showed paraneoplastic (or anti-neuronal) Abs which he did not know anything about and then much later I learned that I tested positive on 7 of the 9 Cell Trend Abs from Germany. If you have any thoughts on my C3 or C4 levels or how they compare to yours, I'd love to learn more about it. On a side note I have to truly thank you (@TrixieStix) b/c in searching to see if I'd been tested for C3 & C4 levels so I could tell you, I found exactly what I was searching for (different test results) that my doctor very much needed for our phone consult tomorrow (and I do not think I ever would have searched the Rheumy tests for these) so you really helped me out without even knowing it!